Are the 2017 Intel iMac no longer in the game?

It seems like I’m no longer able to use versions of UE later than 5.1.1. Not sure why, but here’s a wall I’m run into:

These purple spots are stay even in final render images.



And glass materials are weird, glowing crazy green light all over the place:

Lighting mode “Volumetric NonDirectional” works fine but looks a bit different

Lighting mode “Surface TranslucencyVolume” going crazy

I thought it might be on Apples side, but UE 5.1.1 works fine, and there’s no purple spots and glass works fine.