For all its faults - Youtube has a lot of factual content produced by people who want to share their cool hobbies with the world.
The thing I really want to give up next is Twitter. Or at least my 3,000-follower public account. It started out with finding like-minded friends, but quickly turned into a place where I can't even say "I find WD40 often works better than cutting fluid when machining aluminium" without being jumped on.
By "RI Lectures" do you mean the channel with the actual youtube name of "The Royal Institution"? If so, I think the across the pond competitor is "MIT OpenCourseWare" although I find it far easier to download MIT OCW videos from archive.org than trying to find and stream them and keep track of which I've seen.
I've had the interesting experience of learning Linear Algebra from Strang's textbooks a long time ago, then watching his lectures to refresh my memory. You can do something similar with Automata Theory and Ullman via a MOOC, or at least you could a couple years ago.
Applied Science (Ben Krasnow) is one of my favourites. Cody's fantastic too, for the backyard-science angle. I find Hydraulic Press a bit too "let's break stuff and laugh", but it's fun to watch and switch off for a few spare minutes. Same for Backyard Scientist ;)
Post-Apocalyptic Inventor is good for my scrapyard-challenge-but-real fix.
My real hook at the moment is How To Make Everything. He starts with Stone-age technology and shows the progression from there. It's fascinating to see how we got from "there" to "here" with a series of successive discoveries and refinements.
BosnianBill's Locklab, Locknoob and Lockpicking Lawyer are other favourites (but then, I've always found security tech interesting).
I've got an interest in retrocomputing so LGR, Modern Vintage Gamer, Adrian's Digital Basement and CuriousMarc are on there too.
I do mean the Royal Institution's official Youtube channel, yes. I started watching for Andrew Szydlo's chemistry demos and stayed for the other content!
I've heard of MIT OCW (since the original announcement popping up on Slashdot), but never really looked into what was available. Perhaps I should!
Yes the Hydraulic Press guys have a lot of "boom ha ha" content but they sometimes have more intellectual content such as "We're going to make homemade particle board out of sawdust" and I'm like, no, you're not, I know its way to complicated, but its fun to watch them try and be partially successful.
If you like retrocomputing, then "Moshix" channel will provide a couple hundred hours of mainframe content. The editing is slightly off, moves too slow during non-interactive content such as watching scripts run, and too fast during interactive content while hand editing JCL and typing sysprog tasks in general. Just because you CAN type 100+ wpm doesn't mean its a good idea during a screencast. The content is very compelling, regardless of editing decisions.
Something I don't like about retrocomputing is stuff I started out doing is now considered retro. Or even worse, stuff that was futuristic when I had a couple years in, is also considered retro. I guess getting old beats the alternative.
The thing about YouTube vs regular TV is that _I_ chose what to watch not someone else. I also chose the time to watch it.
Slightly OT, but the host of the original Scrapheap Challenge show is now hosting an EV YouTube channel called "Fully Charged Show" :)
Ms Rogers was very interesting to watch as she is near prototypical "maker culture" in the sense of artist-trying-to-do-STEM (IIRC she's a successful musician) but technically predates popular "maker culture" by about a decade. Sometimes seems old fashioned or retro in 2020, but was extremely futuristic around the turn of the century.