I've recreated the issue on my computer. Opening the macOS Universal app crashes. I'm able to open the Intel only builds of Dolphin, can you? The last dev build was 5.0-15105, and the most recent Dolphin build that included Intel only builds is 5.0-15146.
Something about the Universal app makes it so Dolphin doesn't run on 10.13.6. I can't update any higher because I'm on a Hackintosh and there's no Nvidia support for me after this. You however, can update your Macbook Air to 10.14, 10.15, 10.16, or macOS11. I recommend you do one of those to keep having support for Dolphin.
If you don't want to update, you can stick on the last working version of Dolphin.
If you want to compile Dolphin yourself on your Mac, here are the steps you have to take:
Something about the Universal app makes it so Dolphin doesn't run on 10.13.6. I can't update any higher because I'm on a Hackintosh and there's no Nvidia support for me after this. You however, can update your Macbook Air to 10.14, 10.15, 10.16, or macOS11. I recommend you do one of those to keep having support for Dolphin.
If you don't want to update, you can stick on the last working version of Dolphin.
If you want to compile Dolphin yourself on your Mac, here are the steps you have to take:
Spoiler: (Show Spoiler)

