Using proxy to sync app in an offline qube?

I’m operating from the premise that qubes with networks are compromised or soon to be compromised.

I want to make sure network exposed qubes have no useful data to exfiltrate.

With that in mind I have apps with data I do not want exposed to the network, yet they still need to sync.

I could setup a qube for each and lock down thru firewall settings. This has proved too RAM intensive for my workflow. Right now I’m RAM constrained, and won’t have access to RAM supply anytime soon.

Is there a way to sync an app in an offline qube thru a proxy the way template updates work?