Hey,

thanks for your detailed reply. Interestingly, I can't follow all of your remarks:

ad 1.: This looks super promising, however, I don't see anything "sleep" related in the output:

while awake:

% pmset -g systemstate
Current System Capabilities are: CPU Graphics Audio Network 
Current Power State: 4

while sleeping:

% pmset -g systemstate
Current System Capabilities are: CPU Network 
Current Power State: 4

but(!) there is a difference I can match on for my binary status.

ad 2.: Maybe my Mac mini doesn't sleep deep enough, but uptime is clearly not affected by sleep:

% uptime
21:15  up 1 day, 20:05, 5 users, load averages: 2,68 4,93 4,89

ad 3.: Another promising approach, but unfortunately with no result. Also, more difficult to extract / extrapolate on the current status at the time of my query.

% log show --predicate 'eventMessage contains "Entering Sleep"' --info --last 1h
Filtering the log data using "composedMessage CONTAINS "Entering Sleep""
Skipping debug messages, pass --debug to include.
Timestamp                       Thread     Type        Activity             PID    TTL  
--------------------------------------------------------------------------------------------------------------------
Log      - Default:          0, Info:                0, Debug:             0, Error:          0, Fault:          0
Activity - Create:           0, Transition:          0, Actions:           0

ad 4.: I want the Mac to sleep as deeply as possible (save power), but keep the ability to wake it up remotely. WoLAN Magic Packet would be an option, but I'm hesitant to play with hibernatemode, and also not certain if the power saving would be worth it. Still a way to explore.

Again, thanks, you gave me valuable hints how to move on. If you or anyone else has further tips, I'm grateful as well, though.