Jenkins 2.319.1: master -> "controller" / "built-in node" / "built-in"

Hello,
ok, I understood my problem 1 now better. I’ve been using “…xpath=*/computer/displayName” to get a list of machines, connected to my CI.
I then used these to e.g. check or update stuff on these machines.
So what I “really” need is a way to get a list of machine names.
“displayName” seemed to do the trick (despite I had to “translate” master to the physical node name.)

The labels won’t do the trick, because obviously more than one machine, can (and often will) have the same label attached.

I’ll go hunting for a better way to get this info (“List me all machine names, this CI consists of”).
All hints welcome.

Martin