Most science youtubers have pretty chill comment sections. Same with makers, coffeetubers etc.
Gaming and influencer comments tend to be a shitshow. Obviously.
Nigahiga had chill comment section even with huge following back then. Of course there were negative things on the chat but his whole operations had 'avoid controversy as much as possible' philosophy which made his community generally chill.
I second Vinesauce Vinny. He is just wholesome in general, participates in multiple let's play charities and is just a decent dude. Some chud he worked with tried to cancel him by lying about him and he is known to be so genuinely likeable that the attempt failed miserably.
I remember that. I heard he did it because he was mad about getting kicked out of the group over misusing donations to buy an arcade machine or something. He ended up killing his own career instead.
I hope this doesn't come across as shameless self-advertising, but I am pretty proud of my own followers. (ca. 20k people, the channel is mostly about Breath of the Wild). Compared to the toxic stuff I've seen in other comment sections so far, those guys are super chill and welcoming, discuss with each other in a friendly and respectful manner and want to actively contribute with ideas, questions, their own theories and the like. I've had that channel for three years now and I had to kick out maybe five followers total since then, and two of them were spam bots anyway. Five rude people vs. 20k chill pals seems like a good quota to me ;)
Karen Puzzles is just a bunch of wholesome jigsaw puzzle fans.
Townsends for wholesome 18th Century cooking fans.
Technology Connections for wholesome ELI5 electronics and engineering.
Post 10 for the most wholesome channel focused on unclogging of waterways and culverts you'll ever see. I'm not even joking.
acollierastro, someone called Dr. Collier's channel the "Jenny Nicholson of astrophysics" and thats not even wrong, but is it wholesome? I think so... but decide for your self.
Cracking The Cryptic has a decent community, as might be expected from a channel that mainly solve sudokus and cryptic crosswords. Wirtual (a Trackmania streamer) seems to have a vaguely sane community as those sort of people go.