EDIT Sep 2021: Having crashes again after having a break from flying. Did go in to Radeon software and saw my custom fan curves was gone, card was running very hot but after updating the fan curves I haven’t had a crash in few hours, keeping junction temp at 82-83 with almost max fan speed. It’s loud but it seems to work for now. But getting 3070 very soon so hoping this is the end of crashes.
Have had CTD and game freezing or whole computer freezing up, occurring while running MSFS 2020 after around 10-60min. Can be in menus or in gameplay.
I may have had two separate issues, both seems to be solved. One related to FSE and one related to GPU and AMD drivers & software. Described both solutions below.
COMPUTER SPECS:
CPU: AMD Ryzen 5 3600 (shouldn’t matter)
RAM: 16gb (shouldn’t matter)
GPU: AMD Powercolor Radeon RX 5700 XT, 8gb Red Dragon (THE ISSUE) 
SOLUTION 
(might not work for you.)
Windows 10 game mode: Turned off
AMD Freesync in Radeon software: Turned off (found under “Gaming” and “Display” section in AMD Radeon software)
I also made these two changes but I think they fixed my other issue with game & FSE client crashing.
Dowloand and install latest Visual C++ framework for X86 and X64 ( https://support.microsoft.com/en-in/help/2977003/the-latest-supported-visual-c-downloads )
Run MSFS 2020 as admin.
Hope this can help someone else.
Cheers!
EDIT:
Link to FSE client original solution made by Geealf: https://forums.flightsimulator.com/t/possible-fix-for-game-crash-related-to-net-framework-fseconomy-and-simconnect/269646
Changed the fan speed in AMD software as a safety measure afterwards also, as GPUwas running quite hot, guide found here: How to tune fan speed and cooling using AMD Radeon Software - YouTube