No auto shutdown when idle

Background: I had an old version of LBBox running on a 3B+ which worked just fine for my purposes, but it does seem to work at all in my new Zero 2W (won’t even boot)., so I had to upgrade to the latest version.

I tried setting the Pi to “shutdown when idle” from the webpage, but it never worked – no matter what idle time I set – it just stays on until I manually shut it down. Is there another way to set it to just shut down if it is idle for a few minutes?

In case anyone else also has this problem, the development branch of LBB solves it.