What's the best way to have a continuous backup from Google Photos to an encrypted HDD attached to a Rasberrypi?

So, current setup is a mounted HD encrypted with Veracrypt to a RasberryPi on my home network. Separately, my spouse and I both have Pixel's and all of our photos automatically backup to Google Photos.

What's the most secure/private way to get those photos to sync to my HD as they are uploaded? Doesn't need to be real time, but as close as possible would be nice. Alternatively, maybe there's something I can just use on our phones directly that …

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