Stop unwanted "ON"-time

Sometimes, after a power-out or when Homey accidentally does it, the power switches on in a Z-wave or Zigbee switch.
If that happens, I want to kill that power again automatically (after 2 minutes).

What is the way to go here?

Usually there is a setting in the advanced option of the device itself (not Homey) to change the behaviour when power is interrupted. This should be “revert to previous state” instead of on.

Otherwise, you can enable the Power user experiment in the Homey settings. It will enable a System flow card section with a trigger that happens after Homey reboots. With that you can create a flow to turn everything off. You can put the delay of 2 seconds in that flow for all the actions, or use a timer to trigger a second flow.