Alright, you're hosting on FreeTube (paying for hosting & bandwidth costs) - how are you making money? Most YouTubers don't want to run their own ad network or sell a physical product. Sponsors make deals conditional on YouTube engagement metrics.
Edit: Of course, you do need to have enough demand/scale to make it worth your while, but that will depend on your audience size and how engaged/invested they are in your content AND you personally to an extent. Perhaps be creative and start out with small experiments. Not too hard with LLMs nowadays.
To address the elephant in the room, except for "premium content", you're asking to pay for something the users didn't come for and most probably don't want.
So if you're not into mild grifting, the only way your content is directly monetized is paywalls, and that's an utterly complicated business as you need to show enough to entice, but not too much, while dealing with freebooting and custome support. It can be alleviated by joining a paywalled community like Nebula's, but it comes with it's own issues.
As you point out it's not impossible by any mean, it's just a huge PITA that will make no business sense for most creators compared to ad ridden platforms.
It's very difficult to do this in a way that produces sustainable, durable revenue, and I suspect that people doing technical educational content are finding it increasingly difficult in the age of AI.
Trends for his YouTube channel look pretty much like what I expected given the general trends in the marketplace.
https://socialblade.com/youtube/channel/UCJZv4d5rbIKd4QHMPkc...