First, run hidusb-relay-cmd-setup on the device its connected to.  Ian
Kelling also has a package for openwrt, not yet published.  Ask him if
you are interested.

relay-cmd is a simple script config to use the relay from the device its
connected to. NOT YET TESTED.

libremanage is an overly complicated command that is deprecated. Some
problems with it:

* IMPORTANT: libremanage right now does ssh relay command 1; sleep; ssh
  relay command 2. That whole thing needs to be made into a local script
  or else if the second ssh command fails, the relay stays in the state
  that's supposed to be temporary, making the server impossible to turn
  on without unplugging the relay from it's power and usb ports.
* in the config, most options should have defaults. for managers,
  host/port/username aren't really needed, ssh_config can take care of
  that.
* .libremanage.json should be toml or yaml so it can have comments
* there should be a state command which runs hidusb-relay-cmd state
* The script's function arguments should be made more clear / documented

Background:

GNUtoo has been working on a similar setup. see
https://wiki.parabola.nu/Standalone_BMC. fsf sysadmins, see rt 1346340
for further development ideas.