Perfect! Answers all my questions and thanks for the link.
Edit: No luck, after all. I followed the guide and made sure the Luma settings are correct and that it's loading from the SD. I then installed the TWPatch and made sure those settings were enabled. Also made sure I wasn't forcing DS/DSi mode in the TwilightMenu settings.
GBARunner loads when I select the .nds file within TwilightMenu. However, launching a GBA game just results in a black screen.
Tried each of the two latest gyro releases using the file labeled
GBARunner2_arm7dldi_3ds.nds.
Everything still works in TwilightMenu using the latest update; just no gyro support there.