Most other solutions don't allow pairing of devices across networks.
TFA's "file.pizza" only allows to initiate a session on the device that uploads a file, which makes it tricky to share a file from a mobile device to a laptop (due to tricky QR code scanning with the laptop camera).
PairDrop allows cross network pairing (mobile device can scan QR code from laptop screen), and file uploading from both sides afterwards.
Heh, seeing PairDrop motivated me to make sth similar, but more as a toy/exercise in messing with idiosyncratic/home cooked software:
https://sonnet.io/posts/reactive-hole/
