Self hosted you could use Plex to automatically upload all photos to your computer then download as needed to the other one.
Personally I use Google photos to do this and it works great but will probably require you to get a subscription depending on the size of your library.
My personal phone is android with a work iPhone and I want to transfer things over sometimes so I set up my work phone to upload as well.
I think even the free tier allows for original quality but its been years since I was on it. You only get like 15 GB of space though as well.