Hosts without a .NET Framework installation (e.g. Linux and macOS) have
no GAC; the only system-wide assembly store there is the shared-framework
directory of the runtime executing the decompiler, and
UniversalAssemblyResolver only consulted it through the version <= 4.0
legacy fallback. This made e.g. the type-forwards of a netstandard facade
(pointing to a versioned System.Runtime) unresolvable, which left
well-known types like Nullable<T> without a definition and among other
things misaligned nullability decoding (Nullable<T> occupies no slot in
the nullable metadata, so it must be recognized).
On Windows nothing the GAC answered changes; the new fallback only adds
resolutions that previously failed outright.
Assisted-by: Claude:claude-fable-5:Claude Code
Siegfried Pammer