DAVx⁵ (WebDAV) has been successfully tested with Koofr.

Koofr provides a personal cloud services that also offers WebDAV access.

WebDAV setup

You can access your Koofr files using the DAVx⁵ WebDAV mounts feature.

WebDAV URL: https://app.koofr.net/dav/Koofr

User name and password: your Koofr email address and your app-specific password

To access WebDAV you need to go to Preferences → 2-Step-Verification → "Generate app-password" and use this password when creating the link in DAVx5.