Going forward, the .NET team is using https://github.com/dotnet/runtime to develop the code and issues formerly in this repository.
We do not have plans for new versions of .NETStandard and instead recommend that libraries use the .NET target frameworks like net6.0 and later to get API additions over previous versions of .NETStandard.
For more information see https://devblogs.microsoft.com/dotnet/the-future-of-net-standard/.