Hackable/moddable electronics?

I recently came across a cool video on youtube. https://www.youtube.com/watch?v=dxj8JwdQ7Lk&feature=youtu.be - The guy added a 4g connector to his rc plane and I think some extra batteries and managed to fly to the next island over.

I love stuff like this. Do you guys know any other current electronics that can be modded like this? Sadly it seems like most new consumer electronics come with their own small walled garden and often enough stuff just stops working once the seller goes bankrupt.

Other things that come to mind are:
Raspberry Pi
Arduino
ESP
But do you guys know whole systems that are moddable like this?
The Ryze Tello is a programmable drone, which is pretty cool as well.
I also saw some people modding 3d printers to laser cutters