i test it with my last SDL3 (yeah i work on it) and i build last dhewm3 GITwith it... i just can say... no more crash at exit... completly stable... ARB2 working indeed (with some glish)... but it's completly experimental at this stage i'm not an opengl expert.

i try to build it with last SDL2... but i have always samecrash so maybe SDL2 have problem with dhewm3...

Anyway, if you want Cowcat version working in state, you just need to rebuild it with last SDK of TinyGL and SDL2... but i build it for you:
https://www.morphos-storage.net/upload/test/SDL2/doom3.lha