Quoting Hendrik Boom (hendrik@???):

> But why, why, is a browser listening on a socket that's used for printer
> discovery? Is the browser acting as a printer proxy for everyone on the LAN?
This particular dumbness appears to all about ability to broadcast your
desktop over Google Cast (sometimes called ChromeCast), which uses
Simple Service Discovery Protocol (SSDP) and mDNS. See, you only
_thought_ you wanted to decide what network services are chatting
mindlessly to the world by default. Google, Inc. knows better than you.

https://en.wikipedia.org/wiki/Google_Cast

But you can indeed turn that sucker off, you ingrate. ;->
https://www.vastorigins.com/2019/01/disable-mdns-and-ssdp-discovery-in.html