Autistic young person struggling with feeling good enough

My son is 19 yrs old. He was diagnosed in his early teens. Despite his outward confidence, he struggles with self esteem, confidence and mental health. He feels he is never going to be good enough, not a real man, not as capable as other young people his age, not achieving in the way they do, will never have a relationship or role in this world. He wants to die, but says he isn't even brave enough to make that happen. He's  breaking my heart and I am beyond worried for him. I've tried to explain that lots of 19yr olds feel this way, we don't suddenly turn into an adult when we hit 18! He has no friends, and no desire to go out and meet people. I wish there were safe local groups for young people like him to attend, just to meet similar people and see that he's not alone. We're in the South East and I'm yet to find anything he can attend. He's stuck in online worlds and forums, which I don't think are good for his mental health. Any advice would be gratefully received.