Thanks for the tip. Just tried it and it worked great between MacOS and Android.

Make sure to also try PairDrop https://news.ycombinator.com/item?id=47935875

It's a pretty polished PWA you don't even need to install as it uses WebRTC P2P streaming in the local network or via TURN over internet.

So a good solution for ad-hoc file sharing without ad-hoc network.