Edit: Update! See comment below!
So, this has been going on for a long while now but I hoped after a bit of a hiatus it would maybe fix itself when I come back. Basically, the game does not render any of the close up natural ground textures around a certain radius around me anymore.
It is basically like it stopped rendering the high quality textures for them, as it is literally using the chunk based rendering of the game where it caps out, being affected by zoom / fov levels too. So when I'm in the ship in third person cam and landed, it looks more like a triangle expanding from the cockpit to the back. With the scanner I can even see through the ground and highlight ores or chests beneath, which would normally be blocked, which would tell me that this is within the rendering pipeline of the game.
See album for screenshots & system specs: https://imgur.com/a/CzJTyeV
And no, it is not my GPU. This does not happen in other games, including Fallout NV, and I even switched out to my old RX 580, which showed the exact same problem. It's also not mods, since I tested it on a fresh installation & prefix, with various Proton versions. So at this point I can only assume it must be something with my OS / system config. But when the issue started, I also tried to revert back to an older kernel, which again, did nothing.
I'd really like to avoid trying a new installation of my OS as I'm really sick of going through the backup, restoration & setup process again.
Edit: One detail I forgot to mention. Some single squares do continue to render, even within the invisible radius. But when I go to them and look at the ground, my FPS and frame times start to tank heavily. Unsure if that's related at all though.
I'm amazed that people apparently trust not just sensitive Chinese hardware, such as mobile phones, but even whole Chinese operating systems.