Fvwm3 is a multiple large virtual desktop window manager, originally (a
looooong time ago!) derived from twm.

The successor to fvwm2.

Fvwm3 is intended to have a small memory footprint but a rich feature set, be
extremely customizable and extendible, and have a high degree of Motif mwm
compatibility.

WWW: https://www.fvwm.org/