Hello @ctrl
WebDAV is enabled by default for the Cloudron app version of SFTPGo, it will always be the default port 8888 internally which will bet set each time on app startup.
But, port 8888 is never publicly exposed, so you can only connect via https on the secondary domain.
Unfortunately, it is currently not possible to have secondary domains optional for Cloudron apps.
So either the feature exists or it does not.
In the case of the SFTPGo app this means choosing to offer WebDAV support or to not offer WebDAV support.
We opted to offer the WebDAV support.