We were still using Adium at work until September of 2019.
Most people were on RocketChat, but we’d had a Jabber server up forever, and people were just in the habit. We finally turned it off.
Tangent, sort of: RocketChat is just awful. Push notifications fail, it’s slow, and it just really does not want to mark a message as read. But they insist on having a local on-premises server, so what are you going to do? It’s just so much worse at the basics of chatting than Adium.