It seems like any platform that features link aggregation is soon overrun by bots and self-promoters trying to drive traffic, and pages and pages of link posts versus pages and pages of people talking.
Are there any lemmy instances or other defederated networks that focus on Q&A, niche communities, and people conversing, instead?
tildes.net might be what you are looking for.
but right now it’s invitation only
It’s been invite-only for all five and a half years I’ve been there so I wouldn’t expect that to ever change. Fortunately it’s really easy to get an invite code. Just post in the official subreddit and the mods or another user will give you a code. It’s just enough of a minor roadblock that it helps filter out bad actors.
Personally I prefer Lemmy. But if you’re like OP and looking for conversation focused alternatives tildes is worth joining.