4th and 6th gen intel isn’t too bad yet (which would be early 2010s), especially for a Linux desktop/laptop. I wouldn’t go older than that just because 4th and 6th gen is so readily available for so cheap, but they certainly aren’t anywhere near e-waste yet. Mid-2010s would be more like 7th-9th gen Intel which is newer than all but one of the computers in my home.
I literally use a laptop with a mobile i7-6700 as a daily web browsing computer (and I tend to keep over a hundred tabs open) and really don’t feel any slowness. I’ve got a desktop with an i5-4590 running 5 different Minecraft servers (a couple of which have over 300 mods running) plus most of my homelab services as well. They’re not for the graveyard yet!