Hey Gabriel,
Much of your data about your Windows Admin Center instance is automatically moved over to our new build with the updated backend when you upgrade. However, there's certain data we can't take with us, like proxy credentials and your Azure log-in credentials. We detect if you have any of these items (Proxy, custom Websockets, Azure registration, etc.) configured and only display the information that's relevant to you in the wizard. This migration wizard should appear if you're upgrading from a build that is using the .NET 4.6.2 backend to a build that is using the .NET 8 backend.
I believe the Entra ID issue has been fixed, yes! If you continue hitting issues, please email me.
For HA, we're working on ensuring our implementation is thorough. If there are specific capabilities or features you'd like to see, please let me know. At the latest, HA support should be back in our next major release, but we're hoping to get it out the door much sooner.