Can't start application after upgrading from experimental1 to 1.0

[Slion]

The project creation wizard is still using experimental1 with .NET5 so I worked with that for a while but you can't submit experimental1 to the store so I had to try upgrade.

After upgrading from .NET5 to .NET6 and switching from experimental1 to 1.0 I get the following error when trying to start from the package project:
Unable to find an entry point named 'XamlCheckProcessRequirements' in DLL 'Microsoft.ui.xaml.dll'

Is there something I need to change in package project itself to get that working?
Are there some project creation wizards that are not experimental anymore?

[Slion]

Are there some project creation wizards that are not experimental anymore?

Yes there are, you need to select them in the Visual Studio Installer as explained there:
https://docs.microsoft.com/en-gb/windows/apps/windows-app-sdk/set-up-your-development-environment?tabs=vs-2022-17-1-a%2Cvs-2022-17-1-b#required-workloads-and-components

[Slion]

Is there something I need to change in package project itself to get that working?

Yes there is:

[Slion]

The app launches now. However it crashes as soon as I try to create an extra window. I read about the fact that you could not create an extra window with Windows App Sdk but for me it worked just fine when using experimental1. I can't believe this does not work with the release version. Any tips?

[Slion]

I can't believe this does not work with the release version.

I'll be damned! It works just fine with the experimental1 release but crashes on the stable release:
microsoft/microsoft-ui-xaml#5918 (comment)

That's some questionable release management decision right there…