I think the previous answer may be wrong In our experience it works like below regarding token endpoints

https://login.microsoftonline.com/$YOURTenantName/oauth2/token used for graph api

https://accounts.accesscontrol.windows.net/{tenantId}/tokens/OAuth/2 used for sharepoint rest api v1

for one site app we have x-ms-diagnostics has the value 3002002; reason=App principal does not exist.

other sites and apps are working fine

I think the previous answer may be wrong. In our experience it works like below (regarding token endpoints):

Used for Graph API:

https://login.microsoftonline.com/$YOURTenantName/oauth2/token

Used for SharePoint REST API v1:

https://accounts.accesscontrol.windows.net/{tenantId}/tokens/OAuth/2 

for one site app we have x-ms-diagnostics with the value 3002002; reason=App principal does not exist.

Other sites and apps are working fine.