It's called Tailscale. Here's the homepage: https://tailscale.com
I'd like to see it in the repository because it's a VPN solution that really aligns with the "it just works" philosophy of Solus. Seriously, you just install it, run it, and it works.
The client is open source. It communicates with a closed-source server, but the Linux client is open source.
Here's the most up to date tarball: https://github.com/tailscale/tailscale/archive/refs/tags/v1.18.1.tar.gz
I'll note that in order to comply with their requested build steps, we have to use a git source rather than the tarball.
I've got a working package.yml that I've been using, and as a regular user of the software I volunteer to maintain it should it be accepted.
Thanks!