From the link provided by @paperdigits, I finally succeeded in working either with files from the network share and from the computer, each one represented by a collection.
So now that it proves to work, I’ll attach the external hd to my computer, load all the thousand images into the database, then re-attach the hd to the server, and use the “search filmroll” function with the top-level folder.
I had some hiccups due to permissions stuff because I was mounting the network share on the usual /media folder. So I decided to mount it on my home folder, using this:
sudo mount -t cifs -o username=gustavo,uid=$(id -u),gid=$(id -g) //192.168.y.xx/fotos /home/gustavo/media/gustavo/fotos
With that, even elevating priviledges with sudo, I’m still able to change the mount point ownership to my user so that darktable can write to it.
This opens a whole new world to me, because, so far, I’ve been using only the darkroom. Now I can put all my images under the darktable umbrella.
@guille2306 and @paperdigits, thanks a lot for your help!
EDIT: interesting to note that this way I won’t need an alternative library.