After using samsung tablets for years, i just got a pixel tablet - one motivation was to install GrapheneOS. For the most part, squid works fine, but casting doesn't work without some tinkering:
1. Install squid from the play store
2. Install Google Home from the play store
3. From Google Home, cast the whole screen to your chromecast
4. From squid, tap cast, and choose the second copy of your chromecast that appears.

It should be possible to cast without installing Google Home (VLC and a few other apps are able to with no trouble) so i'm guessing there's just some quirk that might be an easy fix. If not, then at least anyone looking in the knowledge base might find these instructions.