I am wary of anything that seems to good to be true and when i came across a "free" VPN service called ProtonVPN it really did seem to good to be true. At least to me.
You can find a link to the software at:
https://itslinuxfoss.com/category/ubuntu
When you arrive at the site just scroll down until you see "free VPN service".
Would appreciate any other Ubuntu user's thoughts about this software.