ok,
the Nextcloud message is documented as false positive. I had it myself for a while. It can be temporarily removed with:
ucr set ucs/web/overview/entries/service/nextcloud/port_http='80'
To understand the persistent isc-dhcp-client you can throw the log output of:
apt-get -o Debug::pkgAutoRemove=true remove isc-dhcp-client
into a pastebin please, looking for the next step.
Let’s stay careful with apt and its dependencies, and I assume a current backup.
kind regards