I did use nmap on a Linux VM going over the free ProtonVPN for this purpose, but at some point Proton broke something (it may be related to their VPN accelerator feature) and checking any port always reports "Open" (even if it's not), so sadly that made this cool use case entirely useless for me. It definitely was nice to know you had no open ports other than the ones you purposefully opened. :)
I did use nmap on a Linux VM going over the free ProtonVPN for this purpose, but at some point Proton broke something (it may be related to their VPN accelerator feature) and checking any port always reports "Open" (even if it's not), so sadly that made this cool use case entirely useless for me. It definitely was nice to know you had no open ports other than the ones you purposefully opened. :)