mastodon.social Though I too am new there, I like it. It feel refreshing from Twitter’s trash.
Regarding client: I mostly use web on desktop and mobile; though they have official Android app too.
Edit: They are federated with Pixelfed and Kbin too.
I would highly recommend Ubuntu MATE. I just love its simplicity.
Though you may not need, AskUbuntu and UbuntuForums are great places to find help.
I’ve been running Ubuntu MATE alongside Windows 10/11 for many years.