MacBook Pro, 15-inch, 2018.
If you swap option/command modifier keys (in preferences -> keyboard -> modifier keys), then both keys cease to work at all in Factorio. That is, neither option nor command will toggle "alt-mode", and neither option-F nor command-F will search in the crafting GUI.
I originally discovered this because I use an external keyboard (MS sculpt ergo) with modifier keys remapped, but it seems to apply to the Apple internal keyboard also.
[antron] [0.17.2] [keybind] OSX - command/option keys not functional when remapped in system preferences
Re: [0.17.2] OSX - command/option keys not functional when remapped in system preferences
I wasn't able reproduce the problem. I swapped command and option modifier keys in keyboard preferences and the game handled it just fine.
Re: [antron] [0.17.2] [keybind] OSX - command/option keys not functional when remapped in system preferences
This was fixed in 0.17.17.