Tell it to the guy 2 posts above the post You replied to, who had this problem, and to whom I was replying with the aformentioned post.

the no sound firefox bug was present in 17063, wierd that they still didn't fix it

Just few hours before upgrading to 170704 I replugged and configured the Chromecast after some weeks xD.
So now there are two possible casuses, althouth while Chromecast? I am aware of the recent...

On the router it was disabled by default, so I actually tried enabling it with no result, but I didnt try it as You suggest, the other way around, i.e. disabled on both devices, so who knows, maybe...

Build didnt change it so it stayed private as always, I srsly failed to find what this build change to cause the issue, I even checked the DHCP and DNS client windows services whether they were...

Sooo...RIGHT after the system booted with for the first time with build 17074, even though the network configuration is correct (IP/DNS/Default Gateway all correct etc.), even despite that I tried...