I ordered an Enter Keyboard but just noticed that it's not supportive of qmk. But if I just say windows that it is a german layout I should be able to press the keys in the same location as äöü and get the right letters on the screen, right? Or if not is there a mother option to solve my problem? Please say yes otherwise I have to cancel my order.
Not sure how to interpret yout question but:
I do use various keyboards (also Drop ALT & ALT HP) both ISO & ANSI (like Drop Enter) and I'm switching between layouts in Windows/MacOS/Linux with no problems at all, no QMK/VIA/DropConfigurator are necessary, everything is done by OS.
One thing to be aware of:
"äöü" suggest you expect ISO layout (vertical enter) while Drop keyboards are ANSI.
It will still work but ISO layout has one more key than ANSI so one key will not be available to you directly, but should be available via FN layer, if you want to customize FN layer then you'll need to use DropConfigurator or something similar.
krzankWarning: I do not own ENTR so have no experience customizing it, don't even know if it is possible.
But I'm using AKKO 3087 (which has the same layout as ENTR) with FR/DE/RU/AR layouts and it works fine - OS does everything I need.
Appropriate keycaps is another matter.