Latest means of installing Librem One on desktop?
Such as, if Librem One VPN is based on Pia, is there an option of how to use Pia VPN apps?
Is there an option to use Librem One VPN with Windows? I use McDS who blocks Linux sites.
You can use Librem Tunnel with any OpenVPN compatible client. So yes not just GNULinux based Operating systems.
For other platforms you would need the Librem Tunnel credentials, which are different from the Librem One user credentials, and the .ovpn profile file with the cert.
You can see how to obtain them here: https://docs.puri.sm/Librem_One/Generic.html#librem-tunnel
Once you have the credentials and the file, you can import them to a VPN application