I'm literally helping my wife with this as we speak. The 1000 photo at a time limit to download from iCloud is pathetic! Google's solution is SO much better.
Side note - You mentioned Nextcloud... If you're self hosting, take a look at Immich. It's a self-hosted Google Photos clone with Android and iOS apps that has very active development and is insanely quick at loading large photo libraries/thumbnails (unlike Nextcloud).
LG V60 here... My next phone will definitely be the Xperia 1V for that exact reason. Cameras are good enough (and gcam exists) on all flagships now for that to be a non-factor for me. Don't get me wrong, I do want good cameras, but I also want my mSD card, headphone jack, IP rating, wireless charging, and large battery. Name another (new) phone that ticks all those boxes.