Turns out it’s ControlCentre - because by default macs are set up as AirPlay receivers.
$ sudo lsof +c0 -nP -i4TCP:5000 | rg LISTEN
ControlCenter 698 yaleman 10u IPv4 0x431cfa88f6905b65 0t0 TCP *:5000 (LISTEN)
Go into System Settings -> General -> Airdrop & Handoff and turn off “AirPlay Receiver”. You can also just search for “airplay”.
Airplay Settings
$ sudo lsof +c0 -nP -i4TCP:5000 | rg LISTEN | wc -l
0
Fixed!