Hello Wulf,
thanks for the very good explanation.
What I did after upgrading to systemd-43, to find out which packages to reinstall regarding systemd, was:
cave search -m */*::installed -k MYOPTIONS systemd
This gave me all the packages I installed so far with systemd support.
What I did not find out, how to filter the list of packages with names only (no details).
Keep up the great work!
Markus