According to LocalSend docs these are the ports that need to be opened: **Multicast (UDP)**Port: 53317 Address: 224.0.0.167 **HTTP (TCP)**Port: 53317 AFAIK macOS firewall is app-based, at least in the GUI. So depending on how you installed LocalSend, you may have to add it to the list of allowed apps: support.apple.com/en-ca/guide/mac-help/…/mac
You may be able to add the ports above to /etc/pf.conf manually, but AFAIK messing with pf on macOS is not recommended.
The other thing I wanted to ask is about Vallum. If you have it running on that Mac, would it not “take over” the macOS firewall?