Fediverse

Definitely sounds more like a pixelfed use case.

But, any instance can work, just communicate with the admins and make sure it's cool, then create a community and set it to mod only posting. My cousin used to do that, and it worked fine.

There's a couple of communities set up like that as well.

Generally, you won't look like you're spamming posts, unless you're spamming posts. Like, set yourself a time limit between posts, and spread them out.

or do single posts via topic on your personal C/, and include related links/media as comments the way forums did stickied posts for things. Helps keep from reposting stuff too, since you can scroll a thread easier than a C/, on most apps.