The energy level in childhood, brain development, behavioral expectations in school, and everything else is very different. I'm old enough that ADD (now ADHD) wasn't really a thing when I was growing up. People had to learn to manage, without medication. Doing it with medication is different, but being a functioning adult is not the same, and the same knowledge should not applied.
Everything you are saying is from an outside point of view. He sounds depressed, but he went through a traumatic incident. That doesn't mean he cannot have both.
It's not even a little surprising that he had a change in personality. You sound extremely judgmental, to be honest. Your friend went through trauma. He may not have PTSD (that word is used a bit too freely these days), but it was a traumatic experience which sounds like it literally crippled his ability to do half of the things your'e saying he doesn't "want" to do.
He suffered "life long damage to his dominant hand". The hand he presumably uses to help fly the drone, to play music, to use the controller playing games, to use the mouse in Blender (maybe). It may be painful constantly, especially if the rehab/physio was hard to manage during lockdown. You would also have a "large change in personality".
There isn't a lot of psychiatric care which can be done in isolation. People who have ADHD/ASD are also more likely to be depressed, but you can't "root cause" this to a single issue, and saying "well, he's depressed/has trauma, so he should deal with that" doesn't mean he does not also have ADHD.
He is trying to tell himself to "fake it until he makes it" after a traumatic experience, and he does not want to relive the trauma in therapy, he does not want to risk whatever potential side effects from antidepressants.
He is trying to accept that this is his life now. This life of lifelong damage in his dominant hand which has forever put the thing he loves out of his reach, and _maybe_ dragging him out of the house to do new things would introduce him to something new he loves which does not remind him of the life he cannot have anymore. _Maybe_ doing that instead of gossiping with his wife about it and wondering why he no longer does his old hobbies would help.
It sounds as if he is living in limbo between a life he lost and finding new fulfillment. The thing about very traumatic experiences as an adult is that the medication he is currently on (and again, which he probably needs) has made his life somewhat bearable again. He doesn't sound happy, and he doesn't sound like he knows what will make him happy, but the current state of things is so much better than it was two years ago that he doesn't think it's bad, or he worries that making more changes would make it worse again.
Be your friend's friend instead of whatever you're doing now. Monday morning psychiatrist on HackerNews is definitely not.