Its hard to tell if it's a outdated file in the 1.16.5 Resource Pack or something to do with my computer or just a bug in the newest snapshots

I was updating 1.16.5 resource packs to Snapshot 21w20a to immediately discover my screen is all black, enabling your Graphics to Fabulous causes this issue 

I'm not sure how this bug really happens, it seems that using a Resource Pack and having your Graphics enabled to Fabulous will cause your screen to turn black when enabling it in a world, this can still occur even if you don't have a Resource Pack enabled.