Upgrading to LightInject 7.x and LightInject.Microsoft.DependencyInjection 4.x appears to not allow keyed services to be resolved in .NET Standard and .NET Framework. Looking at the source here, it seems like LightInject requires .NET 6 even though Microsoft's DI package can be installed with keyed services support on .NET Framework and .NET Standard?
Keyed services support was released in 8.x of Microsoft DI and that version supports .NET Standard/.NET Framework.