Lots of different channels that I dip in and out of, a few of them already listed that I subscribe to.
I've really gotten into watching this English guy who calls his channel Hambini who's an engineer and tears apart bike firms for their poor craftsmanship while also making his own bottom brackets and finding solutions to problems. If you can stand his language on some of his videos he's really great to watch as he certainly seems to know his stuff and he's able to simplify complex topics.