Is there any built-in oauth2 authorization server available in ktor like spring-oauth2? I was checking the documentation but only found third party integrations.

no builtin server (yet), but what’s wrong with 3rd party tools? I’ve heard this one is okay https://github.com/myndocs/kotlin-oauth2-server

Spring Oauth2 I thought was server side support for Oauth integration? Ktor has that

If you'll be looking at a microservice-oriented architecture, I can't recommend ory/hydra enough. https://github.com/ory/hydra