I am running without gnome (dwm/x11) and have UPower.conf as attached. I have had my librem 15v3 simply poweroff many times between 25-50% batter as reported by /sys/class/power_supply/BAT/capacity.

I will try and have a dmesg -w running and a "watch -n 60 'cat capacity'"and let the power run down to see what happens.

I am using the following script to report battery level to a log:

$ cat /usr/bin/battery
find /sys/class/power_supply -iname "*bat*" -exec cat {}/capacity \;

I use this for my dwm statusbar as well. The path is always /sys/class/power_supply/BAT on my librem but this script works on other linux machines which differ. 👍