Forgot to mention though it may be in the Wiki post.
With Nextcloud app installed it registers itself with the Storage Access Framework. That means your eCloud/Murena files are accessible via the default file manager and any other app that uses the SAF (for opening, saving, backing up, syncing).
But also there is this…
[HOWTO] Use the Account Manager - #14
Haven’t actually tried it with the Murena cloud but it can probably do in a pinch if not using the Nextcloud app.
EDIT: More info…
4. WebDAV Mounts — DAVx⁵ documentation