[pixelface]

there are a number of pieces of electronics that appear to already meet this - high quality (and older) vacuum cleaners, analog audio gear, laboratory equipment, certain kinds of vintage computers.

the main issue i run into with repairs tends to be mask roms / asics / gate arrays that are undocumented and long gone from the market. there are ways around that, but they require great effort. it's only in special niches like arcade machines or iconic 80s synths where people will go so far as to decap and image dies in order to get the needed information.

there is a particular value an object must have in order to tip the scales in favor of repair over replacement. it simply isn't practical to spend a major portion of a device's cost to repair it unless it is special in some way. i place value on repairing things and buying used but a lot of that is out of a personal feeling of pride in repairing and reusing. board level rework is a far cry from changing ones own oil.

on the topic of designing laptops and cell phones to last 50-100 years, you can absolutely make use of communications equipment from 1920-1970. radio teletypes didn't stop working, people still buy and sell them.