It looks like this is a transitive dependency of System.ServiceModel.NetTcp. The PR PowerShell/PowerShell@e069c1d updated System.ServiceModel.NetTcp to a newer version which brought in the transitive dependency of System.ServiceModel.NetFramingBase but as that was never added to the TPA it would fail to be loaded.

I have not verified but this seems to be a regression with 7.6.0 which is when the updated assembly was introduced. While not ideal, a workaround for people using Enter-PSSession to a PowerShell 7 based endpoint is to run this before importing the module

Add-Type -Path "$PSHome\System.ServiceModel.NetFramingBase.dll"

For people relying on JEA with a restricted language mode you can achieve the same thign automatically by adding this to your session configuration (.pssc) file:

@{
    ...
    AssembliesToLoad = @(
        "$PSHome\System.ServiceModel.NetFramingBase.dll"
    )
}

Thanks for raising this! Hopefully it lands soon 🙏

I was testing AssembliesToLoad in the .pssc and I think $PSHome is unnecessary. As long as the entry ends with .dll then GetFileNameWithoutExtension is eventually called on it:
https://github.com/PowerShell/PowerShell/blob/master/src/System.Management.Automation/engine/ExecutionContext.cs#L1419

GitHub

PowerShell/src/System.Management.Automation/engine/ExecutionContext.cs at master · PowerShell/PowerShell

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