We have now support for custom upload scripts. You can write your own upload script and ksnip will call it for you when you hit upload and try to parse the script output. #268

Might be an workaround until this feature is implemented. Check out latest continuous build.

For ftpwe could use QNetWorkAccessManager: https://doc.qt.io/qt-5/qnetworkaccessmanager.html

For sftp we need to use something like libssh: https://stackoverflow.com/questions/13691520/how-to-copy-a-file-in-c-c-with-libssh-and-sftp

Ftp upload added, please test.