Will it work entirely locally? No, account required. Will it work well outside of two happy paths in the demo? Probably no.

... how do you expect a cross-device feature to work locally? 0_o

P2P, you're very likely already in the same network and/or have a bluetooth connection established.

Not counting audio I connect across my devices via Bluetooth maybe once every 3-4 years lol. I don't even think I've ever connected my laptop to my phone. Not to mention even at home I'm not always connected to the same network, for eg one part of my house I don't get wifi properly so might be on mobile data on my phone. I don't think using P2P is particularly noob friendly.

Apple's AirDrop (direct WiFi connection) is pretty noob-friendly though.

Android had "Android Beam" via NFC forever ago, too.

Like KDE Connect which uses only the local network.

A lot of technologies are at hand for P2P communication, which, if you abstract and design it somewhat intuitively, means even more stability and comfort than with just a server.

And no one is saying that there should be no server ever. Forcing a connection to a proprietary server without alternative options is obviously bad, but having a FOSS, self hosteable server with a managed option for non-selfhosters would pretty much be perfect.

• So you'd have an application level, eg. for native functions like a shared clipboard.
• An API level, so third party apps can synchronize/move to other devices.
• A remote device level, which represents all devices you can push data to. Also manages automatic (0/1 click) pairing over NFC and LAN, and manual pairing over Bluetooth, Direct Wifi, and Servers.
• A transport level, which presents NFC, Bluetooth, Direct WiFi, LAN, Server(s) and whatnot as an option for the device level, and manages the availability of transports per device. Transports are chosen based on eg. privacy * speed.

Now I want to implement that shit but have no time to do that :c

Not counting audio I connect across my devices via Bluetooth maybe once every 3-4 years lol.

Hmm, I intermittently pass files among all sorts of non-Apple devices via Bluetooth.