I'm not sure all of these are really small content creators and completely sponsor free but here it is:
YT channel on STEM and making sciency stuff: https://youtube.com/@TechIngredients?si=ic6g-uCLEWXO4DWu
Random technical stuff : https://youtube.com/@TechnologyConnections?si=sz-Gwfgo0gMN3vOG
All things space genuine expert: https://youtube.com/@scottmanley?si=MzE-v1thBOwrvmBf
Great computer stuff: https://youtube.com/@Computerphile?si=S2Ju7aLhViNw5sd8
Not so unnecessary inventions: https://youtube.com/@UnnecessaryInventions?si=O9iy4OVVbhJj6-kE
Some scottish guy researching odd history stuff: https://youtube.com/@CalumRaasay?si=UqgnEsN0YkU7YZuR
This guy sounds ! https://youtube.com/@LOOKMUMNOCOMPUTER?si=9lN-vhpOO-twS6pi
Pretty random list, I just like very different kind of things :)
But I'd say most of the above are passionate people and mostly without ads or sponsors etc.