https://bugs.freedesktop.org/show_bug.cgi?id=107581
--- Comment #9 from Benjamin Hodgetts ben@xnode.org ---
Please try using force_glsl_extensions_warn=true it works around some game bugs.
That generated the two new messages in the terminal...
ATTENTION: default value of option force_glsl_extensions_warn overridden by environment. ATTENTION: option value of option force_glsl_extensions_warn ignored.
... so I assume it was picked up properly, but rendering behaviour didn't change. The nebula clouds were still missing on the loading screen (so space is just black) and in-game looked the same as the screenshot I originally posted (screen is just white except for the menu). All in all, no change.
I'll try with your hack patch and see if that changes behaviour.