I currently use Dropbox to sync entire folders on my desktop/laptop PCs with my mobile devices (and would love to replace this with NextCloud if it were capable of the same). Here’s how my system works currently:
I can take pictures on my phone, which go to a DCIM folder, and everything in that folder is automatically uploaded to Dropbox, and on my wife’s phone that same Dropbox folder gets synchronized with her DCIM folder, so we’re able to share our photo storage automatically. This folder also synchronizes with a virtual machine (in my basement), where I’ve got a script that renames all pictures and video to match the time taken, and places them into folders named by the date taken. Then this synchronizes via Dropbox to our phones. When storage spaces gets low on one of our phones, it’s a simple matter of moving older folders out of Dropbox (into backed up storage) and then Dropbox updates our phones.
The Dropbox PC client syncs entire folders by default, while the Dropbox mobile app requires you to either select each file individually you want uploaded, or use their silly one-way sync functionality that uploads all found pictures on your phone into one folder, and then there’s no way to synchronize external changes back to your phone. I use a third party app called DropSync, which allows you to synchronize entire folders and everything in them with your Dropbox account, in the same way that Dropbox works on PC. I’m curious if this is something the NextCloud app could be designed to do, so I could leave the confines of my DropBox account and host my own using NextCloud.