Also on the Windows Store. If you uninstall the game from Windows (I had it on the start menu so just right click -> uninstall) and then reinstall from the App, it will apply the update correctly and launch in version 1.1.
However, you will ONLY have access to v1.1 with no way to back-rev to any previous patch, so all your previous save files will be completely useless. Paradox has blamed the Microsoft Store for not having a rollback mechanism. However, the fact that they have not developed these updates with backwards compatibility as a software requirement puts the vast majority of the blame on Paradox and is an indictment of their software practices. They seem entirely out of touch with the industry best practices in gaming, who have a standard of releasing major patches AND allowing for previous saves to function in the new environment. The Microsoft Store has its issues as a very naive and minimalist offering, but this poor design is 100% on Paradox for not building a continuum approach to their game.
So our only option as consumers through the Microsoft Store is to start and finish any games as quickly as possible, despite the fact they take many, many hours to complete, because if we don't they will be lost once the next update rolls out. For me, I simply will not be starting any new games since I have no guarantee that I could take them to the endpoint if I can't dedicate consistent time to doing so before the next major patch releases and it is incredibly disheartening to lose the effort put in. Incredibly disappointed with the utter administrative failure displayed by Paradox in this issue, from the timely launch of the patch to the complete lack of available remediation to prevent total loss of effort. Bad form.