

Depends how long is long form for you, if you mean like multi hour videos I have less to give. But for like 25 to 40 minutes videos:
Practical engineering - educational videos about civil engineering.
Dr. Becky - space/astronomy news from an astrophysicist.
Plainly difficult - civil disaster documentaries
Joseph Anderson - gaming essays (multi hour)
Raycevick - gaming essays (around 30min)
The sphere hunter - game essays, mainly classic horror
Jay Foreman - British comedy.
LGR - retro tech deep dives, and tech oddware.
Joe Scott - Did you know, style investigations.
Plus some already mentioned. There is probably more, but keeping this shorter.
Has 9 videos and 0.5M subs, I feel they might be worth looking at!