I store all my photos on a desktop computer and use BackBlaze to automatically keep everything backed up.
It violates the 3-2-1 rule but in the 10ish years I've been using this approach I've had tons of harddrive failures, had to restore some backups due to my own mistakes, but I haven't lost a single image.
I used to do complicated sync stuff but I found that the more moving pieces there were the more I would lose photos for various reasons.