How to install fluxctl on WSL
You could check if someone had made a PPA but it seems unlikely. Also FWIW they publish Windows binaries too, right next to the Linux ones.
I have found very easy steps to install fluxctl in wsl
sudo wget https://github.com/fluxcd/flux/releases/download/1.17.1/fluxctl_windows_amd64 -O /usr/bin/fluxctl && sudo chmod +x /usr/bin/fluxctl$ fluxctl version