Well this sucks. After the main game install went fine and FS2020 launched, then flying about a bit, I went back to the main menu and went to Marketplace where I saw some updates were available. I set them downloading and part way through I had to leave the house. So I shut down the app.
Now when I launch FS2020 I’m stuck on the Checking For Updates screen. I’ve been to Zen Desk and followed all the tips such as reinstalling Gaming Services etc mentioned at this link:
All versions - Stuck on “Checking for Updates” – Microsoft Flight Simulator Support (zendesk.com)
This time a solution is evading me. I have no addons in the Community folder. Again The entire installation experience for this game is terrible. I’d say Asobo’s account log-in and application delivery and update service technology needs work. I’ve been installing games, uninstalling and moving games for Steam, GOG, EA, Ubisoft and Epic all week and the experience in these eco-systems is problem-free. I did in fact spend a few hours moving some Steam games from my fastest SSD to make room for MSFS packages. No issues at all.
I’d say there are just too many dependencies relying on each other in Asobo’s system making it brittle and frustrating. You’ve got account log-in and licensing, Microsoft Gaming Services, Marketplace connectivity, pending updates for Windows OS and Xbox app account dependencies in effect and any problem with one of these will ruin your FS2020 experience, as it’s doing with me right now.
So far the Games as a Service model of FS2020 is more like Games as a Disservice to users 
Two things about this Checking For Updates. Why is it mandatory? Let customers update at their own leisure. Secondly, why is it allowed to enter an infinite loop state? It should timeout with an error code that can be followed up or allow the customer to press ESC to stop the check and update later. I also think Asobo need to introduce their own Verify Packages tool into the product to scan packages folders and allow you to do things such as disable third-party packages and generally detect log and repair problems.