Managed to fix the bug with GetAvailableModes not working. Went back in time and noticed that it was basically broken ever I had completed the port to QDBus, "polished" it up after testing, and committing that changed code. I had decided to try to be clever by specifying the result of the getter as a QList<QList<int>> and it seems that, for whatever reason, QDBus really didn't like that. It doesn't say it doesn't like that, instead it just happily does the codegen similar to my problems with multiple returns on GetCurrentOutputDetails and then leaves it up to you to figure out why. If it was a human, I would say it had a "shit-eating grin" as it willfully performed its duties knowing I would fail. Switching both to use QVariantList does the trick. If you have better ideas, feel free to reach out. Until then, I am happily returning to the saga that is the Display Configuration Batch system.