Everyone has all the top-tier channels listed already, but here are a few good ones that I haven't seen mentioned yet:

Electronics:

Great Scott! (Electronics projects and components), https://youtube.com/c/greatscottlab

Modern Vintage Gamer (Gaming electronics, gaming history, firmware, and reverse engineering topics),
https://youtube.com/c/ModernVintageGamer

Mr. Carson's Lab (Electronics restoration, especially old radios, he has an insane lab),
https://youtube.com/c/MrCarlsonsLab

Astronomy:

Cool Worlds (Similar to PBSSpace time, but very good at statistical analysis and modeling, narrator is very calming),
https://youtube.com/c/CoolWorldsLab

DeepSkyVideos (Catalog of videos explaining different objects of note in astronomy),
https://youtube.com/user/DeepSkyVideos

SciShowSpace (Bite-sized space videos),
https://youtube.com/c/scishowspace

General Science and Engineering:

Undecided with Matt Ferrell (Covers topics that are bleeding edge),
https://youtube.com/c/UndecidedMF

Engineer Guy (Random engineering topics with a few much longer detailed lectures and audio book reads),
https://youtube.com/c/engineerguyvideo

Casual Navigation (Maritime explanation videos),
https://youtube.com/c/CasualNavigation

Microcosmos (Huge selection of microbial life videos)
https://youtube.com/c/microcosmos

Curious Droid (General science and engineering explanations),
https://youtube.com/c/CuriousDroid

Braniac75 (Amateur science experiments, lasers, and random science topics),
https://youtube.com/c/brainiac75

Cody's Lab (Mostly backyard chemistry, but often times has other science experiments),
https://youtube.com/user/theCodyReeder

Seeker (Well produced mini science documentaries and science news),
https://youtube.com/c/Seeker

Quanta Magazine (similar to Seeker),
https://youtube.com/c/QuantaScienceChannel

New Mind (Similar to Seeker and Quanta Magazine),
https://youtube.com/c/NewMind

Periodic Videos (Chemistry and elements),
https://youtube.com/user/periodicvideos

Fermilab (Easily digestible particle physics),
https://youtube.com/c/fermilab

Nils Berglund (Library of particle and wave simulations),
https://youtube.com/c/NilsBerglund

Royal Institution (Huge catolog of science speeches at the Royal Institution),
https://youtube.com/c/TheRoyalInstitution

Ordanance Lab (Explosives science and explosives testing videos),
https://youtube.com/c/OrdnanceLab

Domain of Science (Quantum physics, and he also makes knowldge maps in different science and math disciplines),
https://youtube.com/c/DomainofScience

Alpha Phoenix (Science experiments and materials science),
https://youtube.com/c/AlphaPhoenixChannel

Breaking Taps (DIY materials science)
https://youtube.com/c/BreakingTaps

Mentour Pilot (Aircraft Accident Investigations),
https://youtube.com/c/MentourPilotaviation

Music Theory, Music Electronics, and Synthesizers:

Benn Jordan (General music topics, he has a good scientific mind and electronics skills that he shows off sometimes),
https://youtube.com/c/BennandGear

Adam Neely (Advanced music theory and random music topics),
https://youtube.com/c/AdamNeely

Look Mum No Computer (Music experiments with analog electronics),
https://youtube.com/c/LOOKMUMNOCOMPUTER

Andrew Huang (Random music tech reviews, basic theory, and music production),
https://youtube.com/c/andrewhuang

loopop (The most thorough and comprehensive music electronics feature overviews),
https://youtube.com/c/loopop

Rick Beato (Music production and music industry analysis),
https://youtube.com/c/RickBeato

Tantacrul (Music Software design, he works on Audacity),
https://youtube.com/c/Tantacrul

Math and Computer Science:

Zach Starr (Math and computer science topics),
https://youtube.com/c/zachstar

Numberphile (General math concepts),
https://youtube.com/c/numberphile

Stand-up Maths (General math topics, but goes into more detail than Numberphile),
https://youtube.com/user/standupmaths

Mathologer (General math concepts),
https://youtube.com/c/Mathologer

Steve Yegge (Computer science and software industry),
https://youtube.com/user/SteveYegge

Low Level Learning (Computer science, but the lower levels),
https://youtube.com/c/LowLevelLearning

DEFCONConference (Huge selection of hacking-related talks),
https://youtube.com/user/DEFCONConference

Strange Loop Conference (Software conference videos),
https://youtube.com/c/StrangeLoopConf

Two-mimute papers (Very fast and exuberant machine learning research summaries, hold on to your papers fellow scholars!),
https://youtube.com/c/K%C3%A1rolyZsolnai

Video Editing and Special Effects:

Captain Disillusion (Debunks fake videos with image analysis, and creates walkthroughs of how it's done),
https://youtube.com/c/CaptainDisillusion

Edit, I almost forgot Adam Ragusea, he does excellent science-based cooking videos,
https://youtube.com/user/aragusea