A friend had a gen-1 Chromecast in-box new that they had never used and they gave it to me rather than throw it out.
I would like to stream to it from my N900.

Several questions... (mostly answered in post)

1- is this inviting the corporate cyberpunk NSA/KGB into my home?(YES!) does it force it own network 'calls' home to my enemy Google?(YES!)

2- If this is a network spy, can I neuter this gadget?(YES!!) Maybe a custom user respecting firmware?(see below)

3- if I can neuter this gadget is there a way to do setup with a linux computer or un-googled LineageOS(microG) tablet without ever involving google?(yes, need Teensy AVR dev board, a USB flash drive, and powered OTG cable)

4- If a no-Google setup is possible(it is) is there a way to stream from a Maemo device? What protocol is in use? Is it possible to just hack a crappy python script together or VPN over with the libs we have on our phones already?

To answer most of above, I plan on reflashing with Eureka(need a powered microUSB OTG cable, I can also use it with my N900 and tablet) so I can own this hardware rather than google pwning me and my network.
**Until I can make or buy and deliver a powered OTG cable I am still wondering about a N900 video/audio stream.**
Answers:
If you ever find a new Chromecast DO NOT ever connect or register as the updates may make it unrootable.
How To: Rooting and flashing Eureka firmware(seems mostly or all FOSS GPL v2 or 3 not sure about bin blobs or libs)
https://team-eureka.com/
https://github.com/team-eureka

https://forum.xda-developers.com/sho....php?t=2578653
https://forum.xda-developers.com/sho....php?t=2452838
apparently all tech documentation now has to be on Youtube too so...
https://www.youtube.com/watch?v=A7BedB1AQls

It was my understanding that that the Chromecast uses a proprietary method (or at least an adulterated version of a known protocol) of connecting for streaming and nothing having to do with UPnP or DLNA (I thought it was a version of wifi direct that needed to go through Google servers, but with your post I see it can survive without Google, so I'm not sure...).

I haven't had time to unlock the Chromecast.
I have hopes of poking around the Eureka git and adding something cool like VLC, not sure if VLC server is in the Maemo repos though.
WHat would be best for client/server for video/audio streaming.
I am thinking of this chromecast stick as a better and more universal answer than say the old TRRS to RCA adapter we got with our N900s.
I could see this ending up with a Eureka fork meant for people who just want a private user-respecting pocket size wireless adapter tool to send non-android video to a hotel TV.