I started mma, Jiu jitsu, boxing....
Still hit the weights but just today decided to go back to a bro split as just cant recover.
The martial arts/fighting stuff is great. Does wonders for your fitness, flexibility and ego and you'll meet plenty of new people.
Tinder etc are good for chatting wham, killing time or meeting women. No aggro is it.... Just talk to them. If you get on you get on and can meet. If not unmatched and move on.... People act like it's hard or sad or a hassle, it really isn't any of them, it's just conversation and keeping an eye out.
Night classes could be a shout, work towards that career you always wanted that life got in the way off.
Doorwork for extra money and a social environment is always an option too. I don't do it but I know a few who do.
There's a whole world out there mate, you can do anything on your own frankly. It's just getting past the ego and being afraid of being judged (probably by insignificant people)