I've had a brand new AMD 6950XT (reference design) since about a week now and I'm also having this white flash issue. I think it seems to be related to video playback. I have experienced the white flash while playback of videos, either youtube videos in chrome or local files in VLC. While I myself haven't seen it (yet?) in Steam like the above posted post; that also does seem to be a video.
It's pretty annoying, especially for a product with this price that has already been out well over a year
For the record, I'm using the latest driver 23.4.1 and using a 60hz display (no freesync or anything like that) on Windows 11.
Also, I don't know if it's related or not, but I've also been experiencing some weird green/purple artifacting a couple times. Not at all as 'regular' as the white flashes, but it did raise my eyebrows a bit when it happened (and I have very little 'data' to go by, but it also seemed to be while playing a video).