Can't commission/deploy AMT machines

This is with MAAS 3.5.0~beta1-16222-g.e2a1846c7 running as a snap.

If I add a new machine with AMT BMC, it goes to New instead of Commissioning/Ready.

If I try to commission or deploy such a machine, I get a "Workflow exectution error". Looking at the logs, I see this:

Mar 11 08:48:09 maas-dev maas-agent[1989]: ERR Error executing power command error="exit status 2" ActivityID=1 ActivityType=power-cycle Attempt=1 Namespace=default RunID=ee6d54aa-4e70-48ba-a695-3ca81a460bd1 TaskQueue=agent:power@vlan-3 WorkerID=dkr7yw@agent:1989 WorkflowID=8945263c-0351-4e51-8cda-93fd571cfc33 WorkflowType=power-cycle stderr="usage: maas-power [-h]\n {status,on,cycle,off}\n {amt,apc,dli,eaton,hmc,hmcz,ipmi,manual,moonshot,mscm,msftocs,nova,openbmc,proxmox,raritan,recs_box,redfish,sm15k,ucsm,vmware,webhook,wedge,lxd,virsh}\n ...\nmaas-power: error: unrecognized arguments: --boot-mode pxe\n"