There's an Android app called Sweech that allows you to access your Android device's storage over WiFi, via a web interface on another device on your network.
The app itself is free but you can upgrade to the premium version for $2, which unlocks various other features, including HTTPS and the ability to set a username and password to prevent unauthorized access.
I've been using the premium version for a couple of years now and it's brilliant.
Sweech doesn't actually handle syncing itself but provides you with remote write access to your Android device's storage over your LAN, which gets you more than half way there. You can copy files to or from your Android device, as well as delete them.
I tried with Robocopy but it can't use this type of address (i.e.
https://192.168.1.2:4443/images) as a source or destination.
wget script can handle the actual syncing aspect.