I totally agree with the frustration of having hardware I would like to keep using but can't because it got EOL. Like a smart speaker or something.
But I don't know if there is a pragmatic way to approach that. I mean, I could also say "it should be illegal to produce e-waste", but what does that mean and how do we actually do it?
Where does it end, should EOL windows be open sourced because some software/games/hardware do not work on newer windows versions?
Open source windows 10 would cannibalise Microsoft’s long term objectives.
If you aren't looking at capturing 100% ewaste, then simple laws around liability and penalties for reduced functionality is all you'd need.
Simple things like "if an electronic device, through no fault of the owner, can no longer perform it's main function, then the owner is due a full refund. A company may escape the refund by placing all software required to run the product in the public domain."
It'd miss cases like fly by night companies, but you could catch big players like google disabling their thermostats for non-hardware reasons.