On December 15, 2021 we released version 1.38.0 of OmniSharp which, for the first time, included .NET 6.0 builds of the OmniSharp server. The related feature branch was maintained for over a year, and previously contained a .NET 5-based variant of OmniSharp, though that one was never released.
This is a big milestone in the OmniSharp project as the .NET 6.0 build is much faster and a lot more stable, and is the first step towards retiring the .NET Framework/Mono builds of OmniSharp.