I used my last laptop for 10 years. If you actually want to "Reduce e-waste and extend the life of your existing devices", install a Linux distro with a light DE (e.g i3 or xfce).
I mentioned xfce for that exact reason. It is still pretty light, while being a more familiar to the average user.
That being said, most average users aren't gonna care about e-waste anyways, and are gonna buy a new computer ever couple of years, so for them this is a non-issue.
I use Linux on 10 year old laptops, though typically with minimum 4GB RAM installed. The desktop environment being bloated has been a solved problem for years. Gnome Shell is crisply responsive and Mate (my choice) even more so. Want to watch videos in 1080p fullscreen? No problem.
It's the browser, or rather the stuff that runs in it, that bogs down old laptops. The >1 second delay to switch folders in Gmail, for example, or the sluggish loading of video thumbnails in Youtube.
True. Browsing on that laptop was not a great experience. But the rest of the experience was much better than windows 10 would have been. Instead of 1-2GB RAM usage at idle I was at <500MB with i3.
BTW even latest Lubuntu needs 4GB RAM... Sure you can use minimal window manager like awesome, but not the average joe!