Last week we released version 1.3 of dotnet-script. The latest release introduces support for .NET 6.0 and C# 10 and is available, as usually, through Github releases and on Nuget. You will need to have at least the .NET SDK 6.0.100 installed.
The related language services in OmniSharp (e.g. C# extension for VS Code) have already been updated accordingly a while ago.