If you use non-English languages, you need to localize your system. Normally, localization needs two things: locale support and fonts, but sometimes input method is also needed. If you are newcomer and do not want to set all of these three ( or two ) byy step, you can just read For Newcomers chapter.

For locale suppports, SpiralLinux provides a program to install set, which you can easily find it out-of-box. If there are any problems, you can also install locales-all which provides all locale supoorts, and then edit environment variable to change languages. For example, you can edit /etc/bash.bashrc adding such line:

export LANG=zh_CN.utf8

This will provide Simplified Chinese as default language for you after reboot . You can see the 'code' of your language from locale -a after installing locales-all.

Besides, you need to install fonts so that system can show your language letters or characters, or it will show some strange squares usually called tofu. For most languages, SpiralLinux provides font support out of box. If not, you can install all fonts-noto* packages.

If you used some Asian Languages, or you are multi-langauge user, you may want a input method. Input method (or input method editor, commonly abbreviated as IME or IM) is necessary for some Asian langauge like Chinese or Japanese. It can also used to input some symbols or ancient letters not used today anymore. For most multi languages users, even though swiching keyboard layout is enough, using IME to manage it can be a good choice.

However,installing IM can be kind of complex. For users want to choose and install IM themselves, please read the guidance below. Otherwise, following For Newcomer chapter may be a good choide for you.

If you want to set localiztion ( especially to instal IM ) as easily as possible, do not care about what IM you use, and especially you do not use multi languages, you can simply install task packages for localization. Task packages are like package groups of Fedora or patterns of openSUSE. You can install tasksel to set and install task packages, but use apt to directly install it is also good.

To search task packages, try apt search task-, most task packages here is for fully localization. For example,if you want Japanese, you can use:

apt install --install-recommends task-japanese task-japanese-desktop im-config

If you use gnome, you can also install task-japanese-gnome-desktop; If you use kde, you can also install task-japanese-kde-dekstop.

For other languages users, just change 'japanese' for your own language. im-config is not necessary for those do not use asian languages. Otherwise, you can use im-config to choose IM for you.

In Linux world, there are several IMEs available. Users need to install basic IME framework and specific input methods (sometimes call as addons or engines) according to languages they use and also their habit. SpiralLinux does not pre-install IME due to such complicity, but we prefer a guide to help users to choose and install it.

The specific condition of IM on Debian is kind of different from some other distros, so even those familiar with IM should better read this guide if you never use Debian before.

Note:

1. rime can be used to input most languages but need some config (see Furthermore & Toubleshooting )
2. m17n is a library to support many languages, but usually it is a bad solution
3. table can be used to input many lanugages and symbols but not a good solution too
4. chinese-addons is a fcitx5 metapachage providing most Chinese input method excepting zhuyin/chewing
5. "bad" means it can be support by like rime\m17n\table but there is not any good out-of-box solution
6. fcitx sometimes also called 'fcitx4' to be distinguished from fcitx5. They are maintained by one developer.

1. Use fcitx5 if it supports you language in Debian Stable or flatpak, unless you are on gnome desktop
2. Use ibus if you are on gnome desktop
3. Use ibus or fcitx if your language is not supported well in fcitx5 without using Testing/Sid packages
4. Do not use uim or scim because they are out of date. Few people still using them so there could be many unclear problems
5. Using addon packages from Debian Tesing/Sid can be quite safe, but please not install basic fcitx5 framework from there

im-config is Debian's program to choose IM framework to use. It can help you to auto starting IM when booting and help you to set environment variables. However, if you choose to install fcitx5 from flatpak, im-config cannot work for it, so we have to make a hack. First you need to add flathub repository to flatpak. It should have been added for SpiralLinux out-of-box.

sudo apt install fcitx5-frontend*
sudo flatpak install org.fcitx.Fcitx5 
sudo cp /var/lib/flatpak/exports/share/applications/fcitx5.desktop /etc/xdg/autostart

You may need to check auto start settings of desktop environment, depending on which destop environment you use. Then adding such lines into /etc/bash.bashrc or /etc/environment(x86_64 PC for example):

export GTK_IM_MODULE=fcitx
export QT_IM_MODULE=fcitx
export XMODIFIERS=@im=fcitx
export PATH=$PATH:/usr/lib/x86_64-linux-gnu/libgtk2.0-0:/usr/lib/x86_64-linux-gnu/libgtk-3-0

Then logout from session or just reboot. fcitx5 should work now.

sudo flatpak install org.fcitx.Fcitx5.Addon.ChineseAddons

sudo flatpak install org.fcitx.Fcitx5.Addon.ChineseAddons

Then if you want chewing/zhuyin

sudo flatpak install org.fcitx.Fcitx5.Addon.Zhuyin

or

sudo flatpak install org.fcitx.Fcitx5.Addon.Chewing

zhuyin uses libpinyin project. You can choose one as you like.

Only Mozc available. fcitx5 in flatpak is not a good choice for Japanese users now.

sudo flatpak install org.fcitx.Fcitx5.Addon.Mozc

sudo flatpak install org.fcitx.Fcitx5.Addon.Unikey

sudo flatpak install org.fcitx.Fcitx5.Addon.M17N

sudo flatpak install org.fcitx.Fcitx5.Addon.Rime

sudo apt install --install-recommends fcitx5 im-config

Here --install-recommends is necessary, or fcitx5 on Debian will not work. The major point this Debian makes fcitx5-module-xorg as a individual package, which is differrnt from many distros. Do not forget it. Then use non-root user to run

im-config

You can choose fcitx5 here. Then logout from session or just reboot. fcitx5 should work now.

You can install kde-config-fcitx5 but it is not necessary. You can use kimpanel. It will make IM look much better, but conflict with theme package fcitx5-material-color.

Please install gnome-shell-extension-kimpanel too. This is necessary if you want yo to use fcitx5 on gnome.

If you want some themes, you can install fcitx5-material-color.

Some addons are absent here. That is because fcitx5 is a quite young program so that many of its addons have not been included into Debian stable. You can using packages from Testing or Sid. See Furthermore & Toubleshooting.

sudo apt install --install-recommends fcitx5-chinese-addons

Here --install-recommends may not be necessary but highly recommended.

sudo apt install --install-recommends fcitx5-chinese-addons

Then if you want chewing

sudo apt install --install-recommends fcitx5-chewing

zhuyin using libpinyin is absent here.

You can only install one of there two. However, kkc and anthy are absent here.

sudo apt install --install-recommends fcitx5-mozc fcitx5-ssk

sudo apt install --install-recommends fcitx5-hangul

sudo apt install --install-recommends fcitx5-rime

ibus is probably the most widely used IME in Linux world due to it is highly integrated into gnome desktop. Using ibus on gnome desktop can easily gain a good experience. However, on other desktops it is widely thought that fcixt5 is better. One strong reason to use ibus in SpiralLinux is that in Debian 11 it supports much more languages officially. However, ibus does not support wayland well on non-gnome desktop.

sudo apt install --install-recommends ibus im-config

Then use im-config to set IM framwork and logout or reboot to make it work.

ibus provides most language support in Debian Stable.

If you need pinyin IM:

sudo apt install --install-recommends ibus-linpyin

If you need zhuyin IM, you can choose ibus-libzhuyin or ibus-chewing. Please do not useibus-pinyin and ibus-zhuyin because they are aged and not maintained anymore.

ibus-kkc ibus-ssk ibus-anthy and ibus-mozc are all available here. Just choose what you want.

sudo apt install --install-recommends ibus-hangul

sudo apt install --install-recommends ibus-unikey

sudo apt install --install-recommends ibus-libthai

sudo apt install --install-recommends ibus-rime

sudo apt install --install-recommends ibus-m17n

Please search for ibus-table* packages for extra tables, and ibus-* packages for more IM. If here is no language support of what you want, please think about using fcitx.

fcitx, sometimes also called fcitx4 to be distinguished from fcitx5, is older version that still be maintained now. It does not support wayland. The only reason to use it rather than fcitx5 maybe is it support more addons, especially on Debian 11. It can be the best choice if you need to use languages like Sinhala.

sudo apt install --install-recommends fcitx im-config

Then use im-config to set IM framwork and logout or reboot to make it work.

If you need themes, you can install fcitx-ui* packages.

The package name of fcitx is similar to it of fcitx5. You can search them for yourself. If your lanaguages are not supported, please think about searching your languages under ibus.

"Rime is an input method engine for entering Chinese characters, supporting a wide range of input methods. The Rime engine itself does not provide a frontend for receiving user input. It must be used with an input method framework such as `fcitx5` or `ibus`. " 
——ArchWiki

rime is a IM engine/addon that can be used on various IM framework. As a result, you can use rime on different platforms and operating systems like Windows, Macos and Linux, so that you can get similar input experience on different OS.

One major difference between rime and other IM engine is that it does not limit input schemas. Users can, and actually need, to add input schemas to make it work, although mostly rime-luna-pinyin is used as default.

Thanks to such design, rime can not only provide Chinses input method but also have potential to be a general IM engine. Using rime, you can type any symbols,emoji or other languages if such schemas has been made by any developer. For example, you can make rime-based Greek input schemas on ibus-rime to avoid a known bug of ibusif you use Chinese and Greek on ibus at the same time.

However, to realize this potential, you need to spend much time config rime, especially when you have to make you own schemas. So even though rime provides IM for every langauge in theory, it may not be as powerful in practice.

m17n is a Gnu project to support many languages. However, many IM schemas in m17n is not good for using. Many packages named as xx-m17n even do not provide all the supported languages of m17n, so that it should not be seen as solution when you have other choices.

table actually means "code table". For primary understanding, it can be seen as library of IM. However, for some IM framework, table packages also include some IM engine. For example, fcitx-table-extra provides cangjie which can help to input some strange characters. However, mostly these packages are just for "strange and rare symbols" which are not common used at all, so you should not look upon them as IM solution.

Debian has officical backports repository. However, IM packages are not included. As a result, if you want to use newer fcitx5 packages, you need to install them from Debian Testing or Sid repository.

Please do not add repository directly for apt if you do not want to update your whole system to Testing or Sid, but you can download their .deb packages. Besides, installing IM framework packages is no safe. You may encounter with many problem, especially due to different version of gtk and qt. On the other hand, using addon packages from Sid is much safer, although there is no promised that everything must be OK.

If you have non-English alphabet languages like Greek or Russian in ibus, at the same time you use language like Chinese, you will probably find you cannot activate Chinese input method engine from Greek or Russian. You mmay have to switch to English first then you can switch to Chinese IM to activate it. This known bug is intended to do so, becuase otherwise you may be not able to use Chinese IM with alernative keyboard layout. You have to live with it if you choose to use ibus, unless you decide to use rime to input all languages.