Why cant I see SSDP protocol packets when using Wifi Monitor mode on Ubuntu

edit

I'm looking to snoop on an SSDP conversation between two devices on Wifi. I've set up a WireShark instance on a Ubuntu machine and configured a "Monitor" device using these instructions: https://sandilands.info/sgordon/captu...

However when I now capture via the mon0 device I only see 802.11 protocol packets and can't see any SSDP packets

I had tried just ticking the the "monitor" box on the interfaces list but it would not stay "ticked". The output of iw dev is:

phy#0
        Interface mon0
                ifindex 4
                wdev 0x2
                addr c8:f7:33:8a:dc:07
                type monitor
                txpower 15.00 dBm
        Interface wlp2s0
                ifindex 3
                wdev 0x1
                addr c8:f7:33:8a:dc:07
                type managed
                channel 2 (2417 MHz), width: 20 MHz, center1: 2417 MHz
                txpower 15.00 dBm

Is there away to capture a SSDP conversation in Monitor mode?