Thank you for confirming that the issue is now solved! I also seem to have the issue solved at my side, but forgot to mark this thread as solved.
Bug still present in 1.12.1, affects Win10 18362.10019 (19H2 Slow Build).
NOTE: Insider Build used for this bug. You might want to take a grain of salt since it is an Insider Build, but 19H2 is mostly based on 1903 after all.
I can confirm this bug in 1.12.0 for Windows 10 19H2.
That offer has ended 5 days ago. https://www.pcworld.com/article/3539052/microsofts-free-minecraft-for-windows-10-giveaway-ends-at-midnight-for-java-players.html