(v15, linux)
When changing texture quality the game doesn't change textures properly on the fly after saving the settings (interface textures change to black) and I have to restart the program. Then it's ok.
I'm not sure whether it's a bug, linux specific, or working as intended. In case it's the latter, perhaps when having time you may want to add a dialog prompting the game's restart for the settings to take effect (perhaps two options: restart or revert changes, now it's irreversible).