Going alphabetically and leaving out ones that I think are a bit too niche.
12tone: Videos about music theory and song analysis https://www.youtube.com/channel/UCTUtqcDkzw7bisadh6AOx5w
Atomic Shrimp: Very broad channel with topics as diverse as nature, cookery and scam avoidance. https://www.youtube.com/channel/UCSl5Uxu2LyaoAoMMGp6oTJA
CGPGrey: Gone downhill in recent years but his old stuff is still there. https://www.youtube.com/channel/UC2C_jShtL725hvbm1arSV9w
Design Theory: Recently discovered this channel, videos about product design. https://www.youtube.com/channel/UCdgUN8rX3SEb9L7FDub3I6A
Dr Geoff Lindsey: Linguistics videos focusing on the English language. https://www.youtube.com/channel/UCtFuCBKQTItHCwfHRP9LIjQ
Driver61: Videos on the technical aspects of motor racing; I’m not a huge motor racing fan but I find it interesting. https://www.youtube.com/channel/UCtbLA0YM6EpwUQhFUyPQU9Q
Geoff Marshall: Videos on UK railways and public transport, OK a bit niche but I like Geoff and his enthusiasm. https://www.youtube.com/channel/UCd18OhMfRmjMjzSHP7Zrzmw
Jay Foreman: Comedy education videos on a variety of topics, largely UK-centric but not always. Uploads rarely but it’s always worth the wait. https://www.youtube.com/channel/UCbbQalJ4OaC0oQ0AqRaOJ9g
Kurzgesagt: I think needs no introduction. https://www.youtube.com/channel/UCsXVk37bltHxD1rDPwtNM8Q
Langfocus: Linguistics videos. https://www.youtube.com/channel/UCNhX3WQEkraW3VHPyup8jkQ
Numberphile: Videos on mathematics that I think strikes the right balance of being accessible without dumbing down. https://www.youtube.com/channel/UCoxcjq-8xIDTYp3uz647V5A
Simon Roper: Mostly videos on the history of the English language. https://www.youtube.com/channel/UChnRk6mxWsSOGElm8phdSxw
Tasting History with Max Miller: History told through recreating historic dishes. https://www.youtube.com/channel/UCsaGKqPZnGp_7N80hcHySGQ
The Aesthetic City: Ideas and opinions on archetecture and city planning. https://www.youtube.com/channel/UCX4ppwcUldlxpuiRGoT1INQ
The Tim Traveller: Quirky travel videos about interesting places around Europe, quite nerdy, off-the-beaten-path type stuff. https://www.youtube.com/channel/UC2LVhJH_9cT2XKp0VAfsKOQ
Tom Scott: One of my most enduring favourite YouTubers, no longer active but there’s plenty there. https://www.youtube.com/channel/UCBa659QWEk1AI4Tg--mrJ2A
Veritasium: Very good long-form science videos. https://www.youtube.com/channel/UCHnyfMqiRRG1u-2MsSQLbXA
Wendover Productions (and sister channel Half as Interesting): I guess mainly videos about infrastructure and logistics and stuff. https://www.youtube.com/channel/UC9RM-iSvTu1uPJb8X5yp3EQ
[email protected] - is this the one?