As far as I know, one of the headline features of microblogging networks is searching and following hashtags. On top of that, Mastodon (like Lemmy) tells users that it’s not important what server/instance you join, because of federation.
With Lemmy, I find it easy to search and interact with communities across all the federated instances. Chances are, people on my local instance (even if it’s relatively small) will have already interacted with popular communities for a given topic, so they will be easy to discover. However with Mastodon this concept seems totally broken – when I search a hashtag I want to see everything, and related posts might be spread out over hundreds of small servers for which, apparently, my small server has no content populated. With Lemmy, I understand that content gets populated on my local instance when somebody else on my instance has interacted with it before. I just don’t understand how this approach is feasible with for a system like Mastodon. Maybe I’m misunderstanding something, but it seems like the only way to have a reasonable chance of getting decent results for hashtag searches is to be on the biggest server?
Yes, relay subscription is done at the server level.
That’s probably not really the issue, though. Hashtag search has been severely hampered following the Twitter migration by… People not using hashtags.
This is less a technical issue than it is one of the tool being designed by people who were trying to be an anti-Twitter, and it now bring populated by Twitter users.
The other microblogging platforms on the Fediverse have full text search. Give a Calckey or Akkoma instance a try.