Hi there!
You should not change files in the snap directly.
It might be possible to change this port if it’s possible to change an env var for an installed snap - maybe in your system /etc/environment, for the variable SNAPDEVICEGW_PORT.
That said, please be aware that we don’t test or officially support changing ports for specific services within the store proxy. My recommendation would be to either change your squid’s configuration so it uses a different port (why not the standard 3128?), or if not possible, install the snap-store-proxy on a different machine where the required ports are available.
- Daniel