This article: https://support.sonos.com/s/article/3237?language=en_US
and this one: https://support.sonos.com/s/article/3209?language=en_US
have a section showing the WM: numbers that is a bit confusing.
“WM=0” means your system is in a wired setup
“WM=1” means your system is in a wireless setup
"WM=2" means the device is bonded as a surround speaker or Sub to a Playbar, Playbase, or Beam in wireless setup
My partially wired setup shows WM:0 for all devices, wired, unwired, main or surround/sub.