We went through this with Diaspora years ago because they insisted that following hashtags was the only mechanism they would ever support for what I'll just call "community" posts.

Following hashtags leads towards centralisation because large sites have more easily available and more complete hashtag search results. Then they started coming up with new protocols to relay hashtags and make them more easily collectible and that's when the spam took off.

I said it then and I'll say it now. The better solution is groups - which we've supported in one form or another since about 2010. You can eject bad actors from a group. You cannot eject bad actors from a hashtag.

When you do search hashtags, we've since added features to let you decide what is hashtag abuse or not. A hashtag will match your search if there are less than 'n' total hashtags in the post. You get to define 'n'. From our federated search interfaces a search for #hashtag<5 will returns search results for #hashtag -- only if there are less than 5 total hashtags attached to the post.

In any case we still support hashtag search because our audience demands it. But it's a dead horse. Mastodon has gone the same route as Diaspora because "groups are hard". Yet we've come up with a dozen different ways to federate groups and the FEP process has whittled this down to two contenders.  Mastodon groups are in progress, but they've kind of been in progress for five years. Get with groups people. We've already seen how hashtags end. The fediverse has public groups, private groups and moderated groups today. And as far as I know they all work with Mastodon.

I will caution you to avoid Friendica groups if you're running a raspi or small server. If you follow them, be careful when commenting. Your little garage server for friends and family could suddenly be tasked with delivering a few hundred thousand comments. That was a poor design decision on Friendica's part which I hope gets corrected. (In the interests of full disclosure I created Friendica, but left that project a decade ago to tackle bigger federation issues and have no direct involvement in that project today). Other groups implementations correctly put delivery of large group posts completely in the hands of the large group and not to individual commenters for this very reason. It will literally kill smaller servers.