The boost package updated from 1.78 to 1.79 and this causes the various kea component services to fail to start since kea still depends on boost 1.78.
In the journal typical error message is:
Jun 17 18:42:02 rock64 kea-dhcp4[362]: /usr/bin/kea-dhcp4: error while loading shared libraries: libboost_system.so.1.78.0: cannot open shared object file: No such file or directory
So it is necessary down downgrade the boost and boost-libs package back to 1.78 in order for kea-dhcpe4 and kea-ctrl-agent to run, and that will remain the case until the kea package is updated to depend on boost 1.79.
Please update the kea package to depend on the current version of boost.