After days of trying to fix the CTD in the main menu brought in by Update 5, a very helpful person in a YouTube comment suggested I run my GPU without any OC. Even though my OC is stable in everything else, I’ve set my GPU timings to stock and the main menu has now been running for about 10 minutes without any CTD. Hopefully I can get some flights in now.
I guess the thing is to fix the sim so stable overclocked GPUs will work.
Edit - Important to note I’ve used this OC for the past year, including in MSFS, without a single crash relating to OC instability.