Hi all, I've had this issue for many many months now and had some time at the weekend to run some tests to fix it. The one that actually worked was from @Dr_eam

I went to the main camp to start the quest for the Mastery challenge, got the part where you can select from 3 different missions. Ran through one of them for a few minutes, failed it and spawned back to where you select the missions.

At first all the textures looked fine, but on further inspection, they were kinda flickering. So I tested it again with fast travelling to Lundon to see if that improved it. At first, it was still flickering, but as i hit the objects (such as bushes and tents), the textures were fine. But after hitting a few objects and about 5 minutes of running around, my game is now back to how it was. I wound highly recommend trying this test as it worked for me, but I would expect Ubisoft to officially patch this at some point.

(FLICKERING WARNING - To anyone who suffers from seizures on the video attached or trying to test this in game)