This is a rather strange one and I'm unsure if this is more of a driver issue from nvidia or something with how warframe behaves on these cards, I figured I'd get the ball rolling here to get some ideas on how to fix this or start asking the right people from here. I've observed this ever since I got my 4090fe and randomly different pieces of the ui will start flickering, sometimes even the entire UI will flicker. This is almost entirely seen on the name tags for mods in the foundry, vendor reward lists and the chat bar and menu navigation buttons while in menus. On occasion the entire UI will flicker.
This isn't very consistent but if I sit inside my mod foundry I can watch it happen constantly, it typically lasts for a few seconds and then stops, usually either blanking the whole screen or flickering the mod name tags and menu nav buttons. Typically when it stops something else will start to flicker instead.
Here's a video showing a little bit of what I'm talking about, I'll see if I can get a better example later but this shows it decently