Suppose you’ve got an old PC - for arguments sake, assume a late 2000s PC with only 2GB RAM - which DE would you choose?
Note that whilst a simple WM + some lightweight apps might be a better option, to keep things simple, I’m limiting this poll to just DEs - and too ones which are still being maintained.
Also, in case you’ve voted for a non-obvious/“other” option, I’m curious to hear about your experiences on running that DE on an old machine - and why you’ve selected it over the more obvious choices.
XFCE if you really want low usage. LXQt is roughly on par for CPU/memory usage while having worse UI/UX. XFCE is incredibly polished, from my testing of GNOME, KDE, XFCE, LXQt, TDE, GNOME2 DEs last year. GNOME is the most optimised DE and would be my third pick after LXQt and XFCE for lightweight use. GNOME Debian post boot uses 1.2/4.0 GB RAM for me, just for reference.
You can go for LXQt or Lubuntu distro, if you do want even lesser RAM usage than XFCE.
If you want a very lightweight, extremely polished experience out of the box, Lubuntu or Xubuntu are your best bets. Avoid anything else unless you have plenty Linux knowledge.