How long has it been like that? I've been torrenting via Mullvad for a while and occasionally low-seed torrents take a while to initialize but eventually I get them. Sometimes it means thinking ahead a few days for media that's more niche.
This means having no port-forwarding shouldn't be much of an issue on private trackers (because most people have it to improve their ability to seed) but on public trackers some torrents might not download.
Port forwarding works and you can get a raw wireguard config to dockerize it.
For general use in e.g. open hotspots I still use mullvad/mozilla vpn as I trust them more. (And can pay cashfor mullvad)