Just go to online-go.com in your preferred browser. It works great on mobile. There’s a large collection of puzzles to do. Those are user submitted, which means the quality varies, but some people have put together some pretty good sets that work as tutorials for beginners.
OGS is the most popular server outside of Asia, and has a nice social side with chat rooms and… clubs? I don’t remember their name for it, but you can join groups for finding teaching games, groups for people in your geographic region, etc.
I don’t log on often these days, but I love teaching new players. Feel free to add me as a friend there (and maybe dm me here so I know to look). My name there is nomadfarmer.