Immich is a fantastic photo backup service that is a replacement for Google Photos both in form and function.

There’s a demo at demo.immich.app to see what it looks like and what you can do with it. As far as self hosting stuff goes it’s relatively easy to setup. Work through the setup guide and see if you can understand that to get it running.

What it will do is make it available on any devices on your local (WiFi or wired) network. You will need to open a port on the Linux box’s firewall, but that step is easy and I can show you how to do that on Mint. Then you’ll be able to connect to it from your phone or any other devices (or right from a browser right on the server).

If you have any questions feel free to ask. I have a few things running on a Mint server I have.