I would definitely start by asking him what he’s interested in. Maybe you can find a program in his area of interest so that he has something to help him engage with others. If in person is too much to start, you might be able to find something online where he could talk to people that way. It might feel safer because if he gets too overwhelmed, he can click out of it in 2 seconds. I also tell people to look online for special needs events within a reasonable driving distance or call a special needs school near you, and ask if they have any out of school programs that could help him to learn social skills, and connect. Don’t let the “special needs” title scare you. Autism is obviously a spectrum, so it could help him to be with people on his same level.

Look at library for chess club or painting club or such like