We have a lot of groups on Signal. Linux and FOSS, Veganism, Cafe (general chat), Politics groups, Gaming, Anime (kinda dead), Privacy tips and discussion, Maths, music, open street maps groups, self discipline and procrastination, piracy, language and linguistics, and a few more. If anyone wants a link to join any of these groups, send me a DM.
Signal uses usernames, now. Your phone number will not be public.
Ideally, I would say Matrix is a better option. I am in a few Matrix channel, but not a lot of people use Lemmy there.
I see Spider-Man