I've tried this on two different Arch machines with the same result.
My default $LANG is "sv_SE.UTF-8".
Launching the game with this gives an instant crash.
sphereFACE version RC 14.1.14471.79769 master:f8b1a885 Release for 64bit Linux Compiled Mar 14 2017 00:37:11 with GCC 6.3.0 20170205 and Boost 1_63 .... LanguageStorm: Language sv_SE not available, falling back to sv LanguageStorm: Default language is Swedish (sv). ... New game started Fading in... FPSStorm: Framerate now capped to 60FPS (0.0166667 seconds). Player stats: deaths 0 Player stats: shots fired / hit / accuracy 0 / 0 / n/a Player stats: worlds completed 0 Player stats: portals entered 0 Player stats: weapons collected 0 Player stats: powerups collected / killed 0 / 0 Saving settings to sphereFACE.cfg Settings saved successfully. Saving theme to sphereFACE.theme Theme saved successfully. Not saving - currently disabled. Player ship destroyed. InputStorm: Shutting down. FlockStorm: Shutting down. SoundStorm: Shutting down... SoundStorm: Device shutdown complete. SoundStorm: Stopping streamer thread... SoundStorm: Shutdown complete. Exception: wstring_convert::from_bytes
Full log attached.
Prefixing with env LANG="sv" or env LANG="sv_SE" gives:
LanguageStorm: Unable to obtain system locale, falling back to default LanguageStorm: Default language is British English (en_GB).
The game runs fine in English so I'm not putting this as critical now.
I can't tell what happens on Windows because I can't get debug output, but the game always launches in English even though Swedish is the only available interface language.