Install Fvwm

To install Fvwm3, you can either use your distribution's package manager (if available) or build it from source using meson. The meson build system is preferred, but autotools are available for older systems. Dependencies include development packages specific to your distribution, and optionally Docker for building within a container.

Core and Optional dependences, check it here:
https://github.com/fvwmorg/fvwm3/blob/main/INSTALL.md

Download from GitHub and install:

git clone https://github.com/fvwmorg/fvwm3.git
cd fvwm3
meson setup --prefix=/usr -Dmandoc=true -Dhtmldoc=true build
ninja -C build
sudo meson install -C build