Added mentioned appwrite name servers at my registrar
And added sub CNAME and CAA records in appwrite itself and all the records were propagated successfully
Please check my issue
TL;DR
Developers' custom domain is stuck at "Generating certificate". They have shared details over DM. They added Appwrite nameservers at their registrar and set up CNAME and CAA records successfully. Solution: Review the shared details and check the issue.