RealRTCW won't run (ioRTCW, Debian 12)

[arrowJW]

Running MX Linux (Debian 12), I installed ioRTCW via flatpak and copied the RTCW game files and it ran just fine. But whenever I unzip the RealRTCW files in it, I get this error where, after I skip the intro videos, all I find is a black screen where the cursor leaves afterimages whenever I move it around. The only other thing I can do is open and close the console.

I tried installing ioRTCW straight from the zip file but I got the same error.