I'd like to explicitly forbid UPnP port mapping.
--igd disabled have the same effect as setting
--no-igd? From https://monerodocs.org/interacting/monerod-reference/ :
--no-igd: Disable UPnP port mapping on the router ("Internet Gateway Device"). Add this option to improve security if you are not behind a NAT (you can bind directly to public IP or you run through Tor).
--igd: Set UPnP port mapping on the router ("Internet Gateway Device"). One of: disabled | enabled | delayed (=delayed by default). Relevant if you are behind NAT and want to accept incoming P2P network connections. The delayed value means it will wait for incoming connections in hope UPnP may not be necessary. After a while w/o incoming connections found it will attempt to map ports with UPnP. If you know you need UPnP change it to enabled to fast track the process.