When a Linux app is detecting language based on the operating system environment, it appears that this environment language variable can be modified for the app session like this:

LANGUAGE=cs_CZ /home/user/apps/session-desktop-linux-x86_64-*.AppImage
It launches the Session .AppImage while setting the language to czech.

I am wondering if this would work also for other apps..

echo "LC_ALL $LC_ALL";echo "LANGUAGE $LANGUAGE";echo "LANG $LANG"
may return environment values:
LC_ALL
LANGUAGE en_US:en
LANG en_US.UTF-8