Oh OP I’m one that’s all for this!
I’ve tried to read through the whole thread but might have missed the odd comment, so apologies for any repetition from me.
Firstly on YouTube, there are some really interesting chefs and cooks that have their own channels, plus food vloggers who travel around filming foods from different restaurants, street food markets etc. If he’s not there already, he might find these really interesting. You can set up his account and manage it, put it into ‘restricted mode’ (not perfect but helps to filter out the obviously adult stuff), and help him find some cooks/chefs/vloggers. There’s probably a list out there somewhere with recommendations, I’m lazy so I just look at random of videos rather than having a carefully cultivated list 
but I do like Binging with Babish and Bon Appetit. I sometimes watch Tasty videos (find they’re variable), and I search for different food travel videos (at the moment I’m going through a phase of watching different teppanyaki vids...).
In terms of him filming, take your time to get to know about video production. No one expects perfection but YouTube content has come such a long way, amateurs also have good beginner equipment. Eg maybe a good digital camera (Go Pros are popular but can be pricey), or at least a high quality smart phone for recording video. Most people have an additional microphone, Blue Yeti is the popular starting mic around £100 - not sure how that would work in a kitchen if he wanted to speak whilst cooking (it’s a USB mic so needs plugging into a computer or laptop to record) but would be good for doing audio over if he films first then records his audio over the top. However I’ve seen a number of YouTube foodies using clip on mics so if you do some research there might be a particular one that works well, and plugs into a smart phone or similar.
I’m not suggesting you go full on into attempting professional recording or anything! Just that a decent image and audio makes such a big difference when you put out a video, especially with something like cooking where there can be quite a bit of environmental noise from ovens, boiling, frying, etc. The other element is some basic editing, as he may want to speed up some bits or chop stuff out and such. Basically to get something watchable there’s a fair bit of background work to do, it’s not too hard but if he’s interested in cooking and not at all interested in video editing, audio editing etc then either he won’t enjoy doing it or you’ll need to take that on.
A decent smartphone could just do the whole job and you upload it direct, but just to highlight that even a lot of amateur and child channels have a lot of this behind them. Also, you can disable comments if you wanted to upload and are worried, or if you kept them you can flag anything you think is inappropriate and perhaps monitor/filter what you let him read of the comments. YouTube is extra wary with child content now because of issues in the past so they step in fairly quickly if there’s anything that concerns them, either in the video or the comments, once they’re aware.
Massive derail on YouTube there but saw you mention it and thought I’d add what I can. On a similar note, there are some interesting food bloggers and cooks online too (ie not YouTube, with their own websites) if he hasn’t explored that side yet. That’s also another thing he could do if he wanted, to blog rather than video, and take pictures of food and his cooking steps. A bit easier to do than filming and editing, and a lot more control over whether you allow comments and moderating what people post if you do.
On a separate note, my DH was exactly the same as a child and still is as an adult. He chose not to pursue it professionally, he prefers to keep it as is hobby (he developed a second rather different interest, with similar passion and perseverance, which is what he chose to do for a living). I see a lot of comments around socialising but honestly, I think we as adults can overthink this sometimes. As long as children are encouraged to develop social skills, such as through school or other means (and your DS is, both by being at school and through doing a sport), then that’s more than enough IMO. Some people (like myself, and my DH) are introverted and prefer doing other things, we’ve still managed to work, make friends, get married... DH still spends his free time cooking and on his other interest (the one which is also his career), I spend my free time on my personal interests too (a mix of cooking and another area, but I’ve never been as precise or chef-like as DH!), we’re both happy people with a family and friends, we don’t do big socialising events or regular nights out/get togethers and that’s just fine! It sounds like you’re focused on his wellbeing and ensuring he knows that he doesn’t have to cook, and it’s great he is being supported in his passion.
Good luck to him 