Transparent proxy for incus guests

What method would you recommend to establish a transparent http/https proxy between incus guests and internet?
Guests are on a bridge and a squid proxy is located on one of them.

One container will be designated as the proxy and it would be configured in one of the few ways to be accessible over the Internet on ports 80 and 443.

Then, the proxy would be configured as usual to serve the individual websites in the other containers.

I would like to have a transparent proxy, without must to configure other hosts.

Use example without incus involved: Transparent Proxying

What you need then, is how to get a container to get access to the Internet through a third container. That is, how to block access to the Internet for a container, and force it to use a designated gateway to a third container, the transparent proxy.