Generally, in my experience, modifying the backing storage for a nextcloud instance is more of a PITA than its worth. I would just mount the webDAV in your file manager. This way the nextcloud db stays in sync with the backing storage.

If you are going to be making direct modifications to the backing storage, check this form post on modifying the nextcloud config to have it look for changes on the filesystem.

As for the permission side of things, run ls -lh in the folder that you want to make changes and see what the user:group is for ownership of the existing files and make sure your new files match. Chmod and chown will be your friends here and chmod has a --reference option that let's you mirror permissions from an existing file, a real time saver.

Hopefully this helps!

Easiest way would be to use the Nextcloud desktop app which will mount your Nextcloud and present them inside nautilus for you to do as you wish.

I'm guessing you're talking about the client, right? The data folder on the server shouldn't be touched or modified, except by Nextcloud.

Check who owns the folder. I'll assume the folder is at ~/Nextcloud, but if it's not, just substitute in the path to the Nextcloud folder.

You can check who owns the folder using ls:

ls -la ~/Nextcloud

This should give you something like:

drwx------ 10 user group    4096 2024-03-04 00:00 Nextcloud

Where the word "user" is in the above example should be the name of the owner of the directory. Where the word "group" is should be the group.

If either is root, check to make sure the Nextcloud client is not running as root (using sudo or otherwise).

Otherwise, give yourself ownership of the directory:

sudo chown username:username -R ~/Nextcloud

Replace username with your username.