mDNS Insight

mDNS Insight listens to multicast DNS (mDNS, also known as Bonjour or
Zeroconf) on the local network, and lists each device it finds along with
the DNS-SD services it advertises: printers, speakers, smart home hubs,
file shares and anything else that announces itself. It decodes what
those services say about themselves, so a printer's TXT records read as a
model name and a list of paper sizes rather than a wall of key=value
pairs.

Open it from your desktop's application menu to watch the network live in
a web UI that opens in your browser. Or run it from a terminal:

 mdns-insight                        # discover for a while, then report

 mdns-insight -output-format=json    # the same report, for scripts

 mdns-insight -webui                 # the live web UI, no browser

 mdns-insight -open                  # the live web UI, in your browser

The web UI listens on this computer only, at a port the system picks.
-webui=ADDR serves it elsewhere, for example to reach it from another
machine on a network you trust.