As in, channels where the presenter is laid back, calming, and the content is slower paced and chill. My go two examples are LGR for retro computer stuff, and Hainbach for experimental tape music.
Joe Pera: https://m.youtube.com/@JoePeraComedy In theory comedy, but the most wholesome relaxing kind you can imagine.
WAY OUT WEST with Sandra and Tim, Kind of a farm / homestead in Western Ireland. https://m.youtube.com/@WayOutWestx2
Pretty much exactly Bob Ross if he were a nice Canadian lady doing nails…
Bill Hammack - TheEngineeringGuy
All manner of engineering gadgets and phenomena explained clearly and calmly.
All licenced as CC BY.
Easily Brutalmoose, or his VODs at Moose2. Watching him play Nancy Drew games or old Windows 98 games is the perfect backdrop to working from home.
Another one is a James Channel. Upbeat, nice guy with insane technical experience does crazy stuff like make a SNES console run on an NES console. And it works. (Mostly)
He doesn’t really talk in his videos, but I really enjoy watching Philippe Faraut sculpt in clay. Guy has masterful technique.
I recommend Technology Connections to anyone who enjoys learning about how stuff works. I really appreciate the way this guy explains things for laypeople.
SummoningSalt is super interesting if you like learning about speedrunning. My only gripe is that the videos are all really chill, but tend to have clips of people breaking world records and flipping out, like “FUCK YEAAAAAAAHH WOOOOOOO FUCK YEAH LET’S FUCKING GOOOOO FUUUUUUCK” and it can be very jarring, lol. But I do enjoy seeing those clips in the videos.
Grand Illusions is a fun channel where an older British gentleman named Tim presents curiosities, puzzles, toys, and the like.
Honorable mention: while I don’t watch many of his videos these days, Smarter Every Day is fantastic STEM content
LockPickingLawyer
Steve Wallis (Camping With Steve)
Math Queen
Cathode Ray Dude
City Planner Plays is quite literally the Bob Ross of city building games. He uses his actual professional knowledge of city planning to build really creative and compelling stuff, and he makes it seem easy enough that you want to try doing it yourself. He has commissioned a library of chill lofi beats that he plays in the background of all his videos, which adds to the vibe immensely. And on top of that, he seems like a sincerely pleasant guy, just having fun doing a thing he enjoys doing. It’s an absolute gem of a channel.
Michael MJD: Retro tech youtuber with a very calming voice and video style. Often installs operating systems on unusual devices.
Techmoan: Tech youtuber focused on old audio equipment.
Ashens: British Youtuber, who has been reviewing mostly poundshop tat and occasionally other random items in front of a brown sofa since 2006.
Geowizard: British Youtuber who does online Geography quizzes like Geoguessr and sometimes goes on adventures. The former part is probably more relevant to your question, though even his adventures have a nice, calm narration and music (that he wrote himself).
The Trek Planner: Finds interesting spots on Google Earth and hikes there, usually in the deserts of the Western US. Videos are usually more focused on the journey than the destination, so there will always be lots of nice views of nature. Honorable mention also to Desert Drifter, who did similar videos but unfortunately passed away recently.
Second Geowizard. Chill British dude.
His Geo Detective bits are exactly what OP is looking for. No competition, just using his knowledge, skills, and luck to help people find things, usually from historical pictures of their loved ones.
Bernadette Banner - Historical handmade clothes and sewing tips
Food Wishes with Chef John. Very fun, laid back, and dare I even say informative if you’re into cooking.
I revisit his channel every year at Thanksgiving when I need to prepare a turkey. His super simple roasted turkey video has served me well the last 5 or 6 years.
I always feel so reassured when you get to that one tricky step and Chef John says “But if you didn’t, that’s ok! It’s still gonna taste really, really good!”
Florian Gadsby has an amazing channel for pottery. I find it incredibly relaxing and he is an amazing potter.