Please if you aren't backing up your cloud storage photos/important files, stop reading HN and go and set it up now.
I can recommend backblaze for cheap reliable storage and the restic backup client which is brilliant (a single, small binary). There's also rclone, or even the backblaze cli client. [Sorry I sound like a Backblaze shill!]
I haven't seen any alternatives to Google Photos either. Ente might be most promising, but their iOS app is not great at actually automatically uploading photos.
There are some situations where you may have entered geolocation data on the app/website and this will end up in the json file rather than embedded in the image file metadata. It's up to you to work out how you want to merge this back in.
I recommend everyone who hasn't done it before, to hit the above url while logged in and firing off an export. It will respond back after some time with URLs you can download. Great for downloading your Youtube playlists and history.
The way I do it is slightly roundabout but works well — I sync to iCloud, which in turn syncs to my desktop, which I backup to my NAS from there.
(Important note: You'll need to turn on "Download Originals to this Mac" in Photo's Settings, otherwise you'll get hi-res proxies rather than bit-for-bit source images.)
https://apps.apple.com/us/app/photobackup-backup-photos-and-...
I run it as a cron on my NAS, and the only intereaction I need to have with it is to give it a new 2FA code every ~2-3 months. Highly recommend it
[1]: https://github.com/icloud-photos-downloader/icloud_photos_do...
Also, after reading this I'm going to have to think about what would happen if someone stole my phone. I take it everywhere with me. It's not an iPhone, but it's still worth a few hundred dollars and it has all kinds of data and logged-in accounts on it. I assume if it was stolen at gunpoint, I wouldn't be in a position to refuse to unlock it and unlock some apps/accounts.