I should add a button to copy the decklist in one click and a button to copy only the missing cards.
The code is already under the function "function copyBBDeck()" in "decklist_formatter.html", so modifying "deck.html" should be easy.

I wanted to add the Penny Dreadful format. I've forked the repository to work on it: https://codeberg.org/LifeSymbiont/Best-MTG-Deck

.title() is widely used in the project, resulting in bad capitalization: "Chandra'S Defeat" in place of "Chandra's Defeat". Changing all .title() instances with something able to recognise saxon genitive would be nice.

https://bestdeckforyou.pythonanywhere.com/decklist_formatter recognizes cards in both English and Italian, but returns them in the original language. They should be returned in English.

Signaled by @khalni.
Deck formatter should split at number of lines, not number of card types.

See at https://bestdeckforyou.pythonanywhere.com/decklist_formatter when insert:

Creatures (6):
2 Witherbloom Apprentice
1 Reckless Amplimancer
1 Oriq Loremage
1 Brackish Trudge
1 Bayou Groff
Sorceries (15):
2 Emergent Sequence
2 Rise Of Extus
2 Mage Hunters' Onslaught
2 Agonizing Remorse
1 Mage Duel
1 Leyline Invocation
1 Hunt For Specimens
1 Go Blank
1 Environmental Sciences
1 Devouring Tendrils
1 Basic Conjuration
Instants (4):
2 Big Play
1 Umbral Juke
1 Infuse With Vitality
Lands (15):
8 Forest
7 Swamp
Sideboard
2 Introduction to Annihilation
1 Expanded Anatomy

User should not need to scroll down and back up. Everything should be on the same level.

Adding the html table preview from "/decklist_formatter" to the deck page would provide users with a comprehensive view of the deck.

I would like to automate the process of getting the data. Specially to have up-to-date prices.

It would be nice to know where did you download the decks, prices, data_types, rarity from. Right now I'm getting it from scryfall bulk data download, but I see some inconsistencies between that data and the one you used. For example the rarity is lower case instead of capitalized and the data_types include the sub-types while the one you provide doesn't. That makes me believe that isn't the data you used and I would have to process it so that it's the same. But I could also download it directly from the same place that you did.

Edit: never mind I've now seen the scraper is at ElLorans/GoldfishScrape. I wish I had seen that before scraping the penny dreadful decks from https://dreadrise.wizzerinus.tk/
Edit2: that scraper only gets the decklists, so I'm still curious about the rest of the data.