This does not work because the installed kolab.list file does not contain a string 'deb https'
The contents of this file are:
deb [signed-by=/etc/apt/trusted.gpg.d/kolab.gpg] https://mirror.apheleia-it.ch/repos/Kolab:/16/Debian_12.0_Plesk_17/ /
Manually setting this to be deb [trusted=yes]...