I have an early one someone gave me and there was a custom ROM that one could flash that let one choose their own DNS servers.[FN1] I actually bought a Teensy 2.0 in order to install the custom ROM, but I never got around to doing it. So now I have an old Chromecast and a Teensy 2.0 I am looking to make use of.

TBH, I always found the Chromecast proposition to be unreasonable: "Look at this neat form factor single board computer you just paid for. Too bad only Google is allowed to have control over it. Sorry, you cannot use this for your own projects because [unspecified]. Google must be allowed to conduct surveilllance and gather data." By comparison, lack of complete control over the RPi GPU is rather easy to ignore. AFAIK, the RPi Foundation is not selling online ad services. Compare the number of cool projects people have done with the RPi versus the Chromecast.

1. I think it used to be possible to force use of different DNS servers via DHCP as well.