1. Hard Reset the phone.
2. Connect phone to internet or WIFI or hotspot.
3. Check if the phone will request for gmail or password previously used.
4. Open SamsungFRP Tool, click on Bypass frp and connect phone with USB.
Download Samsung FRP Tool here.
5. Get another Samsung phone and sign in a Samsung Account.
6. Open Play Store in the Samsung of No 5 and download and install Alliance Shield x.
7. Still with No 5 phone open Settings>> Backup and Restore and back up data.
8. Return to Samsung A12 and open here, click on Google quick search box.
9. Open install Galaxy Store then search and install S9 launcher.
watch video below.
This solution works for all Samsung Galaxy Android 11.