I bought the game while it was on sale, and I tried launching it today. After going through the initial configuration, I ran the game. However, the loading screen was extremely glitchy and flickery to the point that I couldn't see what I was doing. I can't play the game in this state. What do I need to do to fix this?

I'm currently using Windows 10, with an AMD Radeon RX 6800 XT graphics card

I'm not entirely sure what you mean by loading screen as you shouldn't have to do anything during loading.

Anyway I'd suggest you goto http://www.kentie.net and get both the "Unreal engine Direct3D 10 renderer" and "Deus Exe".

The site has instructions on putting the files into the game folder and using them.