Well I hope you can follow the above convo thread and solve the issue. If it doesn't work for you give the details of what failed and where. Though just normally updating garuda with
garuda-update
should do the trick and give an output similar to:
Your default display manager was changed from dm_service to new_dm_service automatically, because the former no longer exists.
replace dm_service with whatever appears there.
If you don't get this message at the end then manual intervention is required.