I am using both NextCloud and ownCloud on my Ubuntu installation.
ownCloud and NextCloud nautilus integration mix up in a strange way.
I used to have ownCloud integration unavailable when I had two contextual menus in NextCloud folder, as explained in my note on April 2021, with no reaction.
Now that I have upgraded the system and reinstalled both, it is the opposite: two identical contextual menu in ownCloud, but I have no Nautilus integration for NextCloud.