I don't use that, but AFAIK on most existing social networks you can follow tags instead of users.
I'm no ActivityPub expert but I'd want a software that does not publish individual user actions to activitystreams, only if they're done on a topic. And then you can only be notified of the action if you subscribe to the topic.
Kinda exactly like how reddit works but without the option to follow user accounts, that came much later.
So I think support needs to be integrated into the software.
Ideally there should be a personal ActivityPub instance implementation, something that doesn't require hosting all Mastodon content and can be easily customized in various ways.