Helm v3.1.0 has not been released. You can read about it at https://github.com/helm/helm/releases/tag/v3.1.0

There was about 3 months between the release of 3.0.0 and 3.1.0. The release of 3.0.0 was a large effort and this was followed conferences and holidays. We are now back into the swing of things and releases should be a little more regular.

Regards,

Matt Farina