when i did backport for my repo i've found the problem
> 107 if [ -d "/etc/apache2/" ] ; then
...
> 117 if [ -n "$2" ] && dpkg --compare-versions "$2" 'lt' '2.4.7-1~' && dpkg --compare-versions "$2" 'ge' '2.4.1-1' ; then
> 118 CUR_MPM=$(a2query -M) || exit 1
command "a2query" will be available only after install the package
it's creates a problems with upgrade from old versions apache
--