How would you have anticipated this to work without being on the same network?

Bluetooth is slow and low range.

Airdrop is proprietary Apple-only.

Transfer via internet is both slower, and potentially expensive for you due to mobile data caps. Worst of all it would require hosting of servers to facilitate the transfer, which is both a point of potential attack and a significant cost for someone to operate, which isn’t really sustainable for a free and open source application.

What would you propose?

I did not downvote you by the way, and I am asking because I am genuinely interested in your thoughts.