I use these 2 apps for universal AirDrop rather than pushing people to Apple
I use these 2 apps for universal AirDrop rather than pushing people to Apple

          
          
That's it—that's the app. You could host your own instance on Docker if you want. And you can and should donate if you find it useful. A few key things from the FAQ:

Snapdrop is peer-to-peer through WebRTC and only uses SnapDrop's hosting for a Signaling Server.
Because it's using WebRTC, files and messages are encrypted on transit. Snapdrop doesn't see the files; "Snapdrop doesn't even use a database," the author writes.
The developer only ever intends to keep this project as a way to send files instantly over local networks and willfully rejects new feature ideas.

Once in a while, the Snapdrop site has failed to load on a device, but I'm not the kind of person who can confidently blame that on the device, local network, ISP, regional network, global DNS quirks, sunspots, or whatever else. I'm glad when it works. If it doesn't work, I can fall back to LocalSend.

    
                  
                

LocalSend, the belt-and-suspenders local transfer system
LocalSend is nearly as simple and focused as SnapDrop, but it doesn't rely on the wider global web for anything and can more ably get around the occasional can't-see-you quirks.
The client is available for just about all the major systems, usually in both app store and unofficial channels (Homebrew, Android side-loading, Flathub, etc.). You can send more kinds of things with one click than on Snapdrop, including folders and photos from a phone's library. If a device doesn't show up, you can manually enter its local IP address to find it (which has worked for me a few times). You can favorite a device, send to multiple devices, send multiple files, send via link, choose to have files automatically accepted and saved to a folder of your choice, and otherwise set up things to your liking. And because it's a locally installed app, you can send files to it through your system's share/send dialogues.
LocalSend says it relies on HTTPS connections and a REST API to send between devices, with a TLS/SSL certificate generated on the fly on each device. As with Snapdrop, you can compile and run LocalSend yourself.
I'll welcome any other suggestions for same-network file sharing in the comments. Both of these apps save me from having to log into web-based file-sharing systems every time I just want to show a funny photo or share a PDF, and for that, I thank them.


          
                  