[mxuribe]

That's interesting! I have a thinkpad t420 that's very likely similkar age to yours, and also ran into the issue you described....but my issue manifested while running Linux Mint 19.something....At which point i had been fed up with Mint (for other reasons, so this was the final straw)...so tried - an loved! - Lubuntu. That machine runs beautifully on Lubuntu 20.04.1 LTS (since when this version came out in 2020). In fact, after moving away from Mint - and gotten other machines - i was going to convert this old thinkpad into a terminal-only sort of server (you know, headless, baby)...But Lubuntu - well specifically LXQT - runs so damn fast and smooth on it, that i kept the desktop environment! I've since added another 8GB, so this machine rockets all things i throw at it with its 16GB...and i credit Lubuntu, specifically LXQT for that blazing speed and rock solid stability (yes, yes, i know the stability is ubuntu, and yes, yes debian all underneath)...My point being: as nice as KDE, Gnome, etc. might be, and as low resource hungry as DEs like XFCE, folks should not dismiss LXQT. It might be closer to feature set to XFCE, but wow, does it run lightweight, fast, and solid!