[greenavocado]

Speculating here based solely on general networking knowledge. You may have "AP Isolation" enabled and/or multicast blocking on your network may be causing problems.

If I was working on KDE Connect I would add a microphone and speaker based pairing system using OFDM modulation lifted from Rattlegram. Each device would share all IP addresses associated with themselves using sound to broadcast the information.

[estimator7292]

Just use Bluetooth. These days it's very uncommon for a PC to not have Bluetooth. More of my PCs have Bluetooth than have microphones.

[greenavocado]

Maybe the Bluetooth connection can be used for IP and port discovery.