This is so badly needed… There is no reasonable alternative to AirDrop, which has a number of problems, and is Mac-only.

Snapdrop[1] works quite well if you're on the same network. It's cross platform, you only need a reasonably recent web browser.

[1] https://snapdrop.net/

"Same network" is usually the hard part...

If you're physically close but not on the same network, please check out https://github.com/spieglt/FlyingCarpet.