That's weird. I'm not on iOS, but on my Android phone auto-upload works mostly well. The only problem is sometimes conflicts happen when network signal is very low or non-existent, but otherwise all photos upload fine.

Does iOS have any kind of battery optimisation for apps which you can turn off for Nextcloud? It's a problem on Android phones, you always have to exclude apps you never want to go to sleep from battery optimisation.

I don't think it has aaaaall of those extensive requirements, but Nextcloud Memories is the closest self hosted thing to GPhotos. I have over 20k photos on it and growing, works brilliantly on a small VPS.

Postfix installed on the server itself. My apps don't send many emails, why go through the complication and cost of hosting email externally?