Actually my gotek is put inside an external drive case, connected to the mobo of this unit (which has a power supply in order to activate and deactivate it). I have also a boot selector which works well with DF0 selected but does not work when DF1 is selected to work as DF0.
I set up gotek both as ds1 and ds0 but does not work when put as DF0 with boot selector, while works fine as DF1 when set up as ds1.
I noticed, also with another external disk drive, that it must receive signal from DF0 before start to work as DF1; this depends from the board of external unit I suppose.
So if I connect the gotek directly to Amiga as DF1 with your cable it should work and boot as DF0 with boot-selector, since there's no the passthrow from external drive board.
But now I have new doubts since you wrote that with your cable when S0 set on Gotek it appears as DF1. When S1 set on Gotek it appears as DF2.
So can it work as DF0 with a boot-selector?