Hashtags do not replace groups.
No one moderates them. They’re easy to hijack and spam. And there’s simply no permanence to them.
Which is why, if you actually want to discuss something, it’s better to tag a group. For example, if you want to be part of an actual PC gaming community on the Fediverse, it’s better to tag @pcgaming@lemmy.ca than #pcgaming.
This needs to be common knowledge because people new to the Fediverse do not know about groups. Hell, I’d say people who have had Mastodon accounts for years still don’t know. And that’s a shame.
@fediverse@lemmy.world
You could subscribe to the Lemmy community by following e.g. @fediverse@lemmy.world from mastodon. If you’re familiar with https://a.gup.pe/ , it’s exactly the same from mastodon. The difference is that with lemmy you can also access without passing through mastodon.