I HIGHLY recommend the Chrisfix Youtube channel. This guy just goes above and beyond in providing an entertaining format to do many of the easy fixes and maintenance item on your car. He deserves every subscription he gets. The videos are so entertaining, I just watch them even if I don't have anything broken on my car.
Here is a video on how to change every fluid in a typical car, he makes it look so easy and it turns out, its not that hard. This alone can extend the reliable life of most modern cars yet many people skip out on many of these fluids because it seems too hard: https://www.youtube.com/watch?v=t7JCh7PHoDc
Another great video is the five fundamental things a car needs to work. He eloquently explains how he managed to repair a free car he got just by following a diagnosis procedure that ensures these five items are operational: https://www.youtube.com/watch?v=PNhuDCVIydw
Some models of cars are much more user friendly than others and every car seems to have a unique set of design quirks that make some parts tricky to work on. Thats where more experienced mechanics must unfortunately do the work. In my case I have learned many common jobs and just leave the more complex stuff to the mechanic(still if you maintain a car well these become less common). If I had a full garage, you bet I'd buy a cheap car and just take the whole thing apart and put it back together to learn how to fix everything. Chrisfix actually has videos on doing more complex stuff like replacing a transmission or repairing rust on your car but its the lack of tools that prevents me from attempting the more complex stuff.
One piece of advice my mechanic gave me was that you want to get a car that is popular with younger people as that results in multiple people uploading Youtube videos on fixing everything on that car.
My main car is a first Gen Mazda 3 and it seems like every nook and cranny of this car is documented on Youtube.
My late father drove a 2005 Chevy Equinox and I have had a lot harder time fixing things on this car because it is just not as well documented.
After watching a lot of the ChrisFix videos and getting the confidence to work on a car ( If I mess up the car I still have other one right?) I bought the Haynes manual for each car. This manual has a lot of essential info and repair procedures for each model. If you can, I'd recommend getting the specific manual for your car.
Finally there was also a campaign years back to create a comprehensive course detailing everything about how a car works. I had pre-ordered the course and it was delivered in 2020. IU haven't started it yet because I just haven't had the urge to(too busy fixing my car with Chrisfix videos and then dealing with other maintenance items around the house). If you are interested in more detailed structured content, check it out: https://www.howacarworks.com/