In my experience when I see an open-source community use something like Zulip, Glitter, Matrix, or Slack it seems inactive relative to an equivalent hypothetical Discord community. I think this outweighs the privacy concerns.

Discord's biggest advantage in my eyes is that it makes it easy to build a critical mass of users. This makes it easy for newcomers to get answers to questions quickly.

It doesn't. You are the one heavily devaluating the need of privacy.

>I hate discord with a passion because I don't want to be data mined by some corporate walled garden.

So your disdain for discord has nothing to do with user experience, ease of use, UI, or anything else someone might consider when actually using the product, but it has to do with the ethics of the hosting company.

I can say I hate Porsche because they benefitted from Nazi regime and I will never drive one for that reason, but I'm not going to try to assert that the Ford Pinto is a better car than the 911.

Yes, "better" means different things to different people.

But Porsche's history is just that, history. If a Porsche 911 would send all my data to Porsche it would not be a very good car in my eyes.

I don't think the UI of Matrix is meaningfully different than the one from Discord though. It's a bit like clothing IMO. Mainstream users are very brand-sensitive. They buy Nike shoes not because they're good quality but because it says Nike on them. I bet it works the same way with services.