When recommending people Linux Desktops for very low hardware in the past it was always stuff luke Lubuntu, Xubuntu, Puppylinux (and way more I know) etc.
Today we should not recommend X.org anymore, and Wayland is also said to be faster.
I have good experiences with KDE, but its not trimmed down in any way.
I was thinking about something like the Raspberry Pi Desktop? They use a set of regular Wayland utilities and the Desktop is probably very reliable and resource efficient.
This would be a great new ublue spin, for low resources. If their license allows it, it should be rebranded and changed to be more standard.
Do you know anything else? And no, no window managers please, had a really buggy experience on Fedora Sway.
Keep an eye on Pop COSMIC. It isn’t ready yet, but I’d give it 4 months and I think it would be a great match for something like rpi.