I decided to skip this build (re: this post), but I have been thinking this UWP app sign in issue a lot.
Theoretically speaking the procedure described below should work, if someone would like to test. No changes are made on PC, all your software and files remain intact. I cannot test as I did not install this build on any machine.
1.) Switch to local account
2.) Press WIN + R to open Run dialog, type %windir%\system32\sysprep\sysprep.exe /oobe / reboot, click OK to force Windows to go through OOBE (Welcome Mode) setup:
3.) Sysprep works a while, within a minute Windows will reboot and starts OOBE:
4.) Skip product key, it's not needed on an already activated machine:
5.) Sign in using your Microsoft account email. If you didn't switch to a local account in step 1, you will be presented this:
If this happens just go back, create a dummy local account and when desktop sign out, sign in with your original Microsoft account, delete the dummy account and start again from step 1.
When on desktop after account has been set up, test if UWP apps work as they should. Regardless if yes or no, sign out, sign in to your original user profile (which for now is a local account), remove / delete the new user account (the one for now using your Microsoft account email), reboot and finally switch your original account back to Microsoft account.
You will be back using your original user account with your Microsoft account email, nothing has changed apart from UWP apps possibly working