In Linux, starting any episode other than the first one crashes the game. It crashes immediately after selecting the difficulty setting.
Same issue tested/happens in Solus and Arch for myself and someone else who tested.
$ ./nblood
NBlood r(?)
Built Feb 15 2019 07:50:30, GCC 8.2.0, 64-bit
Using /home/<me>/Software/NBlood/ for game data
Using /home/<me>/.config/nblood/ for game data
Initializing SDL 2.0.9
Using "x11" video driver
Using "nblood.pk3" as main game data file.
Initializing OSD...
Executing "settings.cfg"
Initializing Build 3D engine
Initializing engine
Loading palettes
Loading translucency table
Loading gamma correction table
Loading tiles
Initialized 96.0M cache
Loading "blood.def"
.
Definitions file "blood.def" loaded in 24 ms.
Loading cosine table
Initializing view subsystem
Initializing status bar
Initializing dynamic fire
Initializing weapon animations
There are 4 demo(s) in the loop
Loading control setup
0 joystick(s) found
Initializing network users
Setting video mode 2560x1440 (32-bpp fullscreen)
Refresh rate: 144Hz
OpenGL information
X.Org Radeon RX Vega (VEGA10, DRM 3.27.0, 4.20.8-110.current, LLVM 7.0.0) 4.5 (Compatibility Profile) Mesa 18.3.3
Opened "textures" as cache file
Initializing sound system
Waiting for network players!
./nblood[0x4516ad]
/usr/lib/haswell/libc.so.6(+0x40560)[0x7f7bbba80560]
./nblood[0x500b54]
./nblood[0x420f38]
./nblood[0x5303dd]
./nblood[0x40f002]
/usr/lib/haswell/libc.so.6(__libc_start_main+0xeb)[0x7f7bbba63bdb]
./nblood[0x41131a]
This is the only info outputted to terminal.