In case other users run into the same issue:
Since September 2019, Rebex components for .NET Compact Framework are no longer available in our standard packages. Instead, we have introduces a separate "Legacy Edition" with separate lifecycle, packages and pricing. For more information, see:
To download a trial for .NET CF, do not click the "Download 30-day free trial" download button. Instead, click "Click here for more trial download options" link or go to the "Download" page and choose "Rebex [ProductName] (Legacy) for .NET Compact Framework (30-day trial)" download.
(On a related note: The b77a5c561934e089
PublicKeyToken indicates a ".NET Framework" DLL. .NET Compact Framework DLLs use 1c4638788972655d
PublicKeyToken instead.)