I have now uninstalled and re-installed MSFT Flight Simulator 2020 (without Addons), and I have the same issue. I’ve also tried to disable all Microsoft startup apps:
This is the Steam version, but I have noticed that all Microsoft Store apps, like Messenger are really slow as well as the Microsoft Store itself. All other apps are behaving normal.
I have re-installed Microsoft Store and the apps as well without seeing any improvement.
The game finally starts after about 30 min when launching, but with only 1fps so unusable. I have also deleted the config file and tried a small 1080p monitor.
I use PC with i7 9700K CPU with RTX 2060 Super.
Any ideas? Might open a ticket with Zendesk?