Electronics --- mikeselectricstuff https://www.youtube.com/channel/UCcs0ZkP_as4PpHDhFcmCHyA tesla500 https://www.youtube.com/channel/UCMdOWi6nBZJ3Q0tHNQIOUVA EEVblog https://www.youtube.com/channel/UC2DjFE7Xf11URZqWBigcVOQ GreatScott! https://www.youtube.com/channel/UC6mIxFTvXkWQVEHPsEdflzQ markusfuller https://www.youtube.com/channel/UCx36Uxaf_LHo635bK6kSCPQ
Metalworking --- This Old Tony https://www.youtube.com/channel/UC5NO8MgTQKHAWXp6z8Xl7yQ Clickspring https://www.youtube.com/channel/UCworsKCR-Sx6R6-BnIjS2MA
Computer history / vintage technology --- Techmoan https://www.youtube.com/channel/UC5I2hjZYiW9gZPVkvzM8_Cw Computerphile https://www.youtube.com/channel/UC9-y-6csu5WGm29I7JiwpnA LGR https://www.youtube.com/channel/UCLx053rWZxCiYWsBETgdKrQ
Mathematics --- Numberphile https://www.youtube.com/channel/UCoxcjq-8xIDTYp3uz647V5A standupmaths https://www.youtube.com/channel/UCSju5G2aFaWMqn-_0YBtq5A
Chemistry --- Periodic Videos https://www.youtube.com/channel/UCtESv1e7ntJaLJYKIO1FoYw
General interesting things --- Tom Scott https://www.youtube.com/channel/UCBa659QWEk1AI4Tg--mrJ2A Wintergatan https://www.youtube.com/channel/UCcXhhVwCT6_WqjkEniejRJQ Curious Droid https://www.youtube.com/channel/UC726J5A0LLFRxQ0SZqr2mYQ engineerguy https://www.youtube.com/channel/UC2bkHVIDjXS7sgrgjFtzOXQ Kurzgesagt – In a Nutshell https://www.youtube.com/channel/UCsXVk37bltHxD1rDPwtNM8Q
I can honestly say that I watch nearly every video that each one of these channels produces. When compliing this list I realised how much time I spend watching passionate people talk about what they love.