Hello,
I know you dont want gui but… why don’t you use the android app (or ios) that can send photo automatically : Using the Nextcloud Android App — Nextcloud Android App 1.0.0 Manual 1.0.0 documentation
If you want, all media taken by camera can be instantly upload on your server (you can chose to keep or delete the original on your phone).
You can use ssh but you complicate your life.
If you want to use ssh from your phone, I know that there are some ssh applications on android store. If you manage to use ssh (scp) to copy file on your server, a simple rights and owner check and occ scan will show the file on NC gui.
I don’t think it is faster than Nextcloud Android app. I think that the fatest way is to transfer with usb key… (if you have a physic access to your server).
If you connect your phone to LAN, your box is smart enough to connect directly to the server through the LAN.
I hope this will help you