Mullvad is trusted. They are pretty open with their policies, exist for a long time already, not involved in any privacy scandals (to my best knowledge), charge flat and fair fee without 60% sales and other dubious marketing practices. It is one of the better VPN providers, not in 5/9 eyes (they are in 14 eyes though), you can buy a subscription with crypto, which (assuming crypto was acquired anonymously too) is a good start for some privacy guarantees.

Pretty much every cyber security professional I know uses Mullvad in one way or another, usually as part of a more complex solution.

But all in all, please bear in mind that VPN is not some magic silver bullet to preserve your privacy and anonymity. With VPNs you basically shift your trust from your ISP to the VPN provider. That trust you put into the provider, it is still a requirement. Not to mention that a good chunk of tracking is happening on a lower level nowadays, so if you use Mullvad on Windows / any Apple device etc. do not expect to become untraceable :)