Why I can not `docker compose` up: could not find an available, non-overlapping IPv4 address pool among the defaults to assign to the network

Question

docker compose -p proj-7 up --detach

I know this related to VPN issues. Thus I decide to create isolated network

networks:
  net:
    internal: true
    driver: bridge

Why docker compose still complains about non-overlapping IPv4 address when this network will not communicate with external world and will be isolated? It can overllap with nothing.

How to create isolated container network so I can run multiple stacks:
docker compose -p proj-7 up --detach
docker compose -p proj-8 up --detach
docker compose -p proj-9 up --detach