jtx Board, an Android app that supports VTODO and VJOURNAL without making major compromises. Synchronization is done over DAVx5 and Nextcloud already fully supports it (there is no web interface for VJOURNAL though). However, you can check it out here: https://jtx.techbee.at/
I use jtx Board and support the initiative to be able to sync VJOURNAL entries over NC. At the moment, I’ll look for other ways to back up my journal entries so they don’t get lost when I lose or break my current mobile device.
As @just said, there are currently no efforts being made by the Nextcloud developers to implement this feature. So the only thing left is for a third party to provide an app or extension, which means you have to do it your self, or maybe you get lucky and someone else does it, and shares it with the community…
However, I’m not sure how easy it would be to implement this. It could as well be that it requires a bit more than just a “little” app.
Loving JTX board and I really home someone builds a vjournal and vnotes app for nextcloud just to at least be able to store the vjournal/vnote data for jtx. It could be called JTX data app and it would just hold the data. Does not even need to be usable as an app.
So, this thread explains why I cannot choose my nextcloud account synced through DAVx to sync my journal entries. That really sucks. And worsen yet, doesn’t look like there are any devs that are showing any interest in making it so. Unfortunately, I am not a developer or I would work on it.