With both the #ActivityPub hashtag and the #Guppe group you'll get best reach on the fedi.
Other than that there's the #SocialHub community to ask, but it also has a great archive of past discussion to search in.
Good starter topic: https://socialhub.activitypub.rocks/t/guide-for-new-activitypub-implementers/479
Other than that I co-maintain 3 fedi-related lists on https://delightful.club with many projects codebases to check out.