BoringTun is unmaintained. There are various forks being developed.

I work at Obscura VPN and faced with boringtun bugs a few years ago we evaluated a few of the forks and switched our client to be based on top of NepTUN (https://github.com/NordSecurity/NepTUN).

I am curious why Mullvad started their own fork rather than building on top of one of the existing ones. It would be nice if there could be reconsolidation somewhere.