This is something I'd love to do except it sounds like you said, it requires some basic knowledge of EE etc. Maybe the basics isn't too hard but with the vast diversity of different types of electronics - it troubles me just thinking about troubleshooting what of the 100s of internal parts could be the issue.
I've done my own repairs for phone screens/boot loop issues etc. but they were considered super easy because they were popular phones (galaxy/iphone) and as such, guides were plentiful on youtube. I can't imagine similar resources would be available for, say, a random branded tv or a blender.
Screen fixes are super easy for phones as it's usually a take apart and replace the cables and put back in deal. Anything remotely difficult was fixing a bootloop issue on a galaxy s4 which required a multimeter to confirm the issue and a soldering iron but again, a guide on the exact issue told me exactly what to do.
but i made a point to emphasise that the majority of problems are blown capacitors
this is a prevalent problem(o) that is easy to diagnose and easy to fix
for the listed examples my only diagnostic tool was my eyes, when a capacitor blows you can tell.. that is it looks like it failed in some way
to replace it you have to desolder two connections and solder in a replacement
the capacitors usually give you all of the information you need right on them: capacitance, rated voltage, positive and negative lead; so without needing to know what those things are or why they are important finding a replacement is straight forward and replacing is plug and play, with a bit of solder, if you keep track of how the original was oriented
but like all things it takes time to get comfortable and you get better with more exposure, which is why i emphasised a desire for basic ee to be a part of early education
first time i worked on a car myself i was driving on the highway and my car just stopped, roadside said it'd take 2 hours to get to me, i was unfamiliar with car mechanics but i thought 'i'll just look at it and see if i can see what's wrong, maybe i can fix it', i popped the hood and looked at the engine, it a took a minute to suss it out but when i found the problem it was glaring, the air intake for the engine had popped off, the screw band had rusted and failed, i just pushed the tubing back on the intake pipe, used a dime to screw the rusted band on enough to get me to a hardware store to replace the screw band
i knew i'd be unable to disassemble the transmission on the side of the highway, the first time i opened a car hood, in less than 2 hours, but those expectations were too exaggerated, all i had to do was push a tube on a pipe
i think repair cafes are less about having an in house solution to all problems and more about having broad solutions to the problems that occur the most, and like a bike cafe it could be a hands on experience where there are people there who can help, showing you how to troubleshoot and repair
I've done my own repairs for phone screens/boot loop issues etc. but they were considered super easy because they were popular phones (galaxy/iphone) and as such, guides were plentiful on youtube. I can't imagine similar resources would be available for, say, a random branded tv or a blender.
Screen fixes are super easy for phones as it's usually a take apart and replace the cables and put back in deal. Anything remotely difficult was fixing a bootloop issue on a galaxy s4 which required a multimeter to confirm the issue and a soldering iron but again, a guide on the exact issue told me exactly what to do.