In case it might be helpful for someone else, this is how I finally got the latest VR update.
- apps & features -> Gaming Services -> advanced options
- Terminate, Repair, Reset
- apps & features -> Microsoft Store -> advanced options
- Terminate, Reset
- apps & features -> Microsoft Flight Simulator -> advanced options
- Terminate, Repair (NOT Reset but Repair!!)
I think it was #6 above that did the trick.
I then fired up MSFS2020 and got a message about a mandatory update which opened up the Microsoft Store and started downloading (1.03GB).