Rename used Magic Keyboard

I bought a used Magic Keyboard to replace the one that came with my 2019 iMac. (Don't ask why, long story...)

The steps in this thread didn't work for me till I combined multiple answers into a single workflow:

FIRST-

go to System Preferences>Accessibility and enable an on-screen Accessibility Keyboard;

THEN:

1 Connect Device

2 Go to settings, right click on device, dont click the menu, leave it open

3 Turn off Device

4 Select "rename" in the still open right click menue

5 rename the device and close the pop up

(meaning: type the name on the Accessibility Keyboard using the Mouse)

6 Turn device back on and wait for it to connect by Bluetooth