Lemmy, Slack, Zulip, Signal
I suppose the messages app on my phone, but that's mostly just receiving SMS notifications.
Privately: Mainly Matrix, and sometimes SMS and phone calls. Also Messenger and Discord for specific people.
For work: Teams, Slack, e-mail and GitLab.
Personal: Signal mostly, for personal chats I do also have Telegram and WhatsApp. I am starting to use Matrix for community chats as I just discovered it.
Work: Microsoft Teams.
Only because my family uses it and won't switch to something more privacy minded, I'm stuck with facebook messenger on my phone. Otherwise, I can't really contact them since it's mostly messages through their accounts and not direct from their numbers.