Existing/running AP server supporting C2S to develop against?

Hi, I am trying to develop an AP client in angular. I need an AP server for that, are there any running public AP servers with implemented C2S API?

AFAIK Mastodon has not C2S implemented (Client to Server support in Mastodon), neither has Pleroma (however we’re discussing this at Want to build an ActivityPub client; where to start?).

Please tell me if you have any tip, thank you!

as noted in the other thread, Pleroma does have C2S

Here, for future reference: Want to build an ActivityPub client; where to start?