Ubuntu automatically suspends the laptop for the background user when switching back to it from the foreground user.

To reproduce:

1. Install Ubuntu 18.04 on a laptop
2. Create two user accounts
3. Login to the first account and switch to the second account
4. Disconnect the power plug and work (while on the battery) from one (or the other) account for some time (more than 20 minutes which is default according to the "gsettings get org.gnome.settings-daemon.plugins.power sleep-inactive-battery-timeout" CLI command)
5. When switching a user back to the other account, it will automatically suspend the laptop.

Workaround:

For each(!) user disable "Automatic suspend" in the Power settings or same with the CLI command:
gsettings set org.gnome.settings-daemon.plugins.power sleep-inactive-battery-type 'nothing'

Bug?

I think it is as having the multiuser session, switching back to the background user it should not immediately force the laptop sleep due to the background user inactivity.

How to solve it?

gnome-settings-daemon should probably not take into account the inactivity timer (or rather reset it) when there are other foreground users are using Ubuntu.