You could use cron to do that I'm guessing.
1. Start an SSH session with your box via command line with a computer
or root@the ip number of your box
(Above is from Linux command line.. might be different using Windows or MAC etc)
type yes for key ( if this is your first time connecting to your box)
Default password should be libreelec.
To my knowledge cron should be running already...
2. Check with:
It should return a 4 or 5 digit number. If it doesn't get back to me... cuz it's not running
I'm just going to assume it is running... for now..
---------------------------------------------------------
3. Change Directory to where cron stores stuff.
cd /storage/.cache/cron/crontabs
make a file here... you can use the nano text editor
4. Type something like this...
(you will enter a text editor)
5. Type this in whilst in the text editor.
55 23 * * * root poweroff
6. Then hit ctrl-X then hit y to save.
If everything goes well.. you box should shutdown at 11:55pm every day.
Perhaps somebody can clarify that poweroff is the proper command to shutdown libre elec properly? (Or is it shutdown which seems to give 1 minute grace with no arguments)
I'm probably clear as pea soup, so ask more questions if you need too.
Hopefully that steers you in the right way.
Cheers,
Gary