Thanks @raymo!!! I have installed LOS17.1. Ones more for all Germans:
Activation of the hardware keyboard QWERTZ and the yellow keys without installation of FinQwerty:
System → Languages and input → Physical keyboard → Builtin keyboard → "German Android keyboard"
System → Keys → EXTRAS: Other keys → Hardware keyboard: Layout "qwertz" and Custom keymap "on"
After that, the key layout works perfectly, including the yellow arrow keys and the yellow special characters, like
! "§ $% & / () =?` @ € µ