I am trying to add a Debian source for apt:
add-apt-repository 'http://ftp.de.debian.org/debian sid main'
but I got this message:
Error: could not find a distribution template for Kali/kali-rolling
Adding repositories to your Kali setup is not recommended and liable to break your system. Kali isn’t a general-purpose distribution, and shouldn’t be used as such; nor is it intended for non-experts (and the fact that you’re asking this question suggests you aren’t).
Furthermore, Debian Sid is currently somewhat broken since it’s undergoing a Perl transition.
In summary: don’t do this.