in fact I would prefer to use old devices with secure firmware, like old thinkpads in practice, with linux obviously
I'll be paranoid..
As someone who's been using an old laptop for many years, I can tell you it becomes more and more challenging. With just 2 CPU cores, even Firefox (with it's threads showing as "Isolate+" in
top) can easily consume both cores. I can only imagine it gets much slower a few years in the future. Websites become more demanding.
This brings me back to my earlier conclusion:
Privacy is cumbersome.
I understand very well but it's not that uncomfortable, it depends on which sites you look at
clearly the sites that have posted all the computation and complexity client side (that is to say all the sites totally in javascript) are a bit heavy
but for the sites I look at, I think a raspberry pi 4 is enough
so it doesn't worry me