Mullvad and a few others have had to disable this feature because it turns out it’s super useful for hosting malware C&C servers, phishing pages, etc
There are other solutions for your use case, with or without a third-party VPN, that wouldn't require port forwarding. There are also other VPN services that do offer this functionality.
>"Unfortunately port forwarding also allows avenues for abuse, which in some cases can result in a far worse experience for the majority of our users. Regrettably individuals have frequently used this feature to host undesirable content and malicious services from ports that are forwarded from our VPN servers. This has led to law enforcement contacting us, our IPs getting blacklisted, and hosting providers cancelling us."
>"The result is that it affects the majority of our users negatively, because they cannot use our service without having services being blocked."
https://mullvad.net/en/blog/removing-the-support-for-forward...