External storage access

I have managed to get access to my external storage device but from within nextcloud I can view but not write. I have set permissions in Ubuntu for users, admin and others to be able to read write etc using Ubuntu file (manager) but I still can’t write to it. In fact even using Ubuntu I can’t write anything to it. Any ideas please ?
Ps why is it so difficult to just add extra storage to my set up using nextcloud.

I think ubuntu mounts external drives as read only by default.