They are claiming ProtonVPN port forwarding only works with Windows, however this is only relevant if you are using protonvpn app.
You can still generate wireguard config with nat-pmp support.
https://protonvpn.com/support/port-forwarding-manual-setup/
https://lemmy.dbzer0.com/post/21703
I ended up buying ProtonVPN. Port forwarding required a bit of trickery with natpmpc image to set up in my case (headless wireguard gateway for dockerized services), however now it's fine and working.
Speeds are at least 800Mbps download (which is maxing out my uplink, vpn is likely to be capable for more), didn't have a chance to test upload.