How's the offline app support? My full library (30k items) is available on my phone (not in high res). There are a lot more concessions I'm sure.
Offline support is alright, though I haven't worried about this much. I think it doesn't do any local deletion, so whatever stays in your DCIM folder is still on device.
Do you have to ever open the app though? On iOS/Android?
In my case I would need it to run on the phones of my family members, and they probably will never open the app.
I decided to try Nextcloud exactly because of this. My problem with it is more that the whole thing is a bit unreliable. Like once in a while the app will get into a state where the only way I found to recover is to just erase everything and re-sync everything. And the app will resend ALL the pictures, even though they are already on the server.
And I can't do that with my family members' phones. It doesn't matter to me if the app takes a month to sync the photos, but it has to require zero maintenance. I can deal with the server side, but I need it to "just work" on the smartphones.
Searching for "nextcloud ios background sync" shows a whole bunch of forum posts and bug reports about it not working well unless you have the application open.
One issue (https://github.com/nextcloud/ios/issues/2225) been open since 2022, seems to still be not working properly. Another (https://github.com/nextcloud/ios/issues/2497) been open since 2023.
For something that works well it seems like a ton of people have a lot of issues with it. Are you sure you're on the latest iOS version? Seems like people experience the issues when they're on a later version.
I think that the forum posts may be old, and/or a bunch of them may come from users who did not know that they had to set the location permission this way (which admittedly is unintuitive for photo syncing).