It’s great that you’re starting from a fresh install, because that makes it easier to debug the issue. But could you please explain very systematically what you have done so far?
Have you tried running:
setxkbmap -layout "de,us"
In the AppVM? If that allows you to type German, then following this post will allow you to make it permanent and across all VMs.
If it doesn’t work, then run sudo dnf install xkeyboard-config and try again.