Yup, and Reddit started in 2005 (which is 2 decades ago now) with its large migration in 2010. Lemmy only really got going in 2023, and it’s growing

Misskey is a Mastodon style platform, that is popular in Japan and existed from a while back. They added activitypub support in 2018

https://en.m.wikipedia.org/wiki/Misskey