Client library for push notifications for app devs

IIRC/AFAIK there was the plan or at least there is the possibility of creating a client library for push notifications for FLOSS apps, so they do not need to include the proprietary GMS/FCM/… library by Google for pushes.

However, I'm not able to find any information about that nor any issue for tracking/following. Also the website does not state anything on that.
If there is one, please apologize this duplicate.

There is of course the one for exposure notifications (https://github.com/microg/GmsCore/issues/1179), but this is not the one I mean.
The GitHub tag/label client library also only seems to refer to that EN feature, does not it?

I also searched the org repos, but only find archived projects, which are/were apparently tries to implement this:

• JGooglePlay
• JGoogle
• GoogleServicesFrameworkIncludes

So what is the current status here?

This library would make the work for many, many FLOSS apps easier that want to get into F-Droid, but are blocked by having a proprietary dependency.
BTW, in any case, a separate repository for that library would be useful (also for EN, if you want to integrate it there, too), so one can easier link to it and show alternatives for app developers.

Start by reviewing the linked exposure notifications issue and the archived JGooglePlay, JGoogle, and GoogleServicesFrameworkIncludes repositories. Determine whether a standalone push-notification client library is planned or already exists, then document the current status and any defined scope for app developers.