I'm using nut wrapper from Martin Lang and have both servers (apcupsd and nut) available for clients. Please see the details here: https://www.reddit.com/r/homelab/comments/ar0h9l/apcupsd_nut_wrapper_script_apcupsd_and_nut_on_the/ For Raspbian I have created script for starting/stoppping the wrapper as a service: nutwrapper.txt It works for my Synology NAS and Domoticz nut plugin just fine.
Note there is a package conflict on Debian, actually comes from the nut-client package, because both provide /etc/init.d/ups-monitor: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=170655 -- I double checked, that's still an issue. You can't install two packages providing the same file, and since nut-server depends on nut-client, you can't install both nut & apcupsd on Debian at the same time to work around this; you can build from source however to bypass packaging and use newest features.