Host Immich on the VM. Enable NFS on the Synology, and mount the shared folder on the VM.

so you're self-hosting a party?

one day it'll be my turn

Instead of an android emulator, you could self-host a 2FA web app like https://github.com/Bubka/2FAuth

For IOS, Swift Paperless

Any database or spreadsheet-type app? Grist comes to mind.