For your specific use case of photos, Immich is the front runner and a much better experience. Sadly for the general Dropbox replacement I haven't found anything either.
I had really good luck with Seafile[0]. It's not a full groupware solution, just primarily a really good file syncing/Dropbox solution.
Upsides are everything worked reliably for me, it was much faster, does chunk-level deduplication and some other things, has native apps for everything, is supported by rclone, has a fuse mount option, supports mounting as a "virtual drive" on Windows, supports publicly sharing files, shared "drives", end-to-end encryption, and practically everything else I'd want out of "file syncing solution".
The only thing I didn't like about it is that it stores all of your data as, essentially, opaque chunks on disk that are pieced together using the data in the database. This is how it achieves the performance, deduplication, and other things I _liked_. However it made me a little nervous that I would have a tough time extracting my data if anything went horribly wrong. I took backups. Nothing ever went horribly wrong over 4 or 5 years of running it. I only stopped because I shelved a lot of my self-hosting for a bit.
It's what I want to try next. Written in go, it looks promising.
A good idea is to have it on an always-on server and add your share as an encrypted one (like you set the password on all your apps but not on the server); this pretty much results in a dropbox-like experience since you have a central place to sync even when your other devices are not online
Let me know if you know of any alternative which have helped you but I haven't tried syncthing but I have heard good things about it overall so I feel like I like it already even if I haven't tried it I guess.
I use it on my phone (configured to only sync on WiFi), laptop (connected 99% of the time), and server (up 100% of the time).
The always-up server/laptop as a "master node" are probably key.
It makes a little more sense when you’re using their cloud version, because otherwise you’re storing the data twice.
I know people work around these iOS limitations by setting up springboard widgets that piggyback on background refresh tasks to do uploads. People also create Automator actions (e.g. run every day at time or location based) in the Shortcuts app.
I haven’t tried it but a popular option on iOS seems to be: https://apps.apple.com/app/photosync-transfer-photos/id41585...
I have it installed on my immediate family's devices to ensure all the photos are auto-backed-up to our NAS (which is then backed up to another NAS).
I need to check to make sure it's still working once in a while (every couple of months), but it's usually fine, and even if it's somehow stopped working, getting it running again catches itself up to where it should have been anyway.
Like if I backup photos from iOS, then remove a subset of those from iOS to make space on the phone (but obviously I want to keep them on the cloud), and later the mobile app gets out of sync, I don't want to end up in a situation where some photos are on iOS, some on the cloud, but none of the devices has everything, and I have no easy way to resync them.
I have had the server itself fail in strange ways where I had to restart it. I had to do a full fresh install once when it got hopelessly confused and I was getting database errors saying records either existed when they shouldn't or didn't exist when they should.
I think I am a pretty skilled sysadmin for these types of things, having both designed and administered very large distributed systems for two decades now, but maybe I am doing things wrong, but I think there are just some gotchas still with the project.
iCloud / Google Photos just don't have that, they really never lose a photo. It's very difficult for me to convince my family to move to something that may lose their data, when iCloud / Google Photos works and is really not that expensive.
client_max_body_size 50000M;
proxy_read_timeout 600s;
proxy_send_timeout 600s;
send_timeout 600s;
FWIW, my library is about 22000 items large. Hope this helps someone.