Yeah I had considered it, as I know it’s a popular topic, but I know virtually nothing about cars.

Would you break out the different sections by manufacturer - is most stuff specific to certain makes/models? Or is it general enough that a “brakes” section would make sense?

There's a body of general knowledge that is applicable to most makes and models, and specific knowledge for each make and model. The specific knowledge is mostly in service manuals and dedicated forums, but the general knowledge is widely available in video form. The general learning path is to get the general background online, then read the service manual for the exact procedure for your car or bike.

Would like to add that 1Aauto does great videos, at least for my 7th generation Honda Civic.