For what it's worth, when I modified the dialer app to add a feature the developer didn't want, I discovered that there is a nag built into every screen that triggers randomly for "unofficial" versions: https://github.com/SimpleMobileTools/Simple-Commons/blob/5ad...
Just to be clear, is apple's icloud photo storage E2EE? From what I've been able to find it isn't, but I couldn't find anything official one way or the other from apple directly.
I have had some trouble with the Pop Shop leaking memory, freezing, and crashing, but you can disable it and use Gnome Software if you want a gui.