I have a 3090 w/ 24G VRAM, it supports flash attention and bf16, but is a bit old. I dont run generative models on it as they would be slow and inaccurate, but I do run embedding models, OCR, and system one (decision) models on it.
Btw, fellow 3090 user, some time ago i saw this: https://github.com/Zagitta/gpu-unlock
Can't try it personally because windows, but maybe it will help you.