Dependencies:

On Debian based OS

enable 32bits repositories

sudo dpkg --add-architecture i386
sudo apt-get update

install fltk 32bit lib and glu 32bit lib

sudo apt install libfltk:i386 libglu1-mesa-dev:i386

enable multilib:

https://wiki.archlinux.org/title/Official_repositories#multilib

install fltk 32bit lib and glu 32bit lib

paru -S lib32-fltk lib32-glu