Mullvad doesn't support port forwarding [1] for users that need it unlike proton vpn [2].

Although I have never needed it myself, which in that case Mullvad might be better since they require minimal registration details.

[1]: https://mullvad.net/en/blog/removing-the-support-for-forward...

[2]: https://protonvpn.com/support/port-forwarding

unless you have a specific use case where you need to run a server through your vpn this isn't as much of a problem as you think it is.

torrents for example have hole punching functionality built into uTP where reachable peers help unreachable peers connect to each other.

I am also a relatively happy proton user (now, but wasn't always this way). I second this. Based off the site, it looks like Mullvad passed a real world test too, Proton has not. I haven't tried Mullvad in a couple of years, but they were always reliable and fast. The only issue I had with Mullvad was getting connected to enough peers when torrenting, especially on older torrents where the pool of users is small. Proton's port forwarding feature did noticeably help with that. I do enjoy being able to pay a discounted yearly subscription price with Proton and their user interface is nice. There are some minor problems with split-tunneling in Proton though, sometimes it doesn't work and I haven't figured out why.