Thanks!
Seems to work now.
What I did (Xiaomi Mix4):
-installed newest ROM 14.0.8.0
-installed Magisk with PlayIntegrityFix according Guideline here
-used deny list and wiped data from Google apps often
--> did not worked. Safety checks always fully red
-uninstalled the PlayIntegrityFix
-uninstalled Magisk
-installed latest APK from link above
-wiped all data from Google apps like wallet, play store and play services
-rebooted
-safety check passed device and basic integrity.
-tried to add a visa card. Seems to work (ING is maintaining the banking system why I can't finished the card in wallet today)
Let's hope that it holds some time
Thanks a lot for now for your help! I assume I will come back