I tried it with a microUSB to USB-C adapter. The starts to boot, then notifies you that the chromecast is not receiving enough power to continue. I unfortunately had to order the $20 adapter
I can confirm that the old adapter does not work with a micro to USB C adapter.
Ethernet works through a cheap USB C mini dock, though.
https://i.imgur.com/R67QQYv.jpg
https://i.imgur.com/t8znRiO.jpg
Edit: that setup was just for testing. I don't actually have it dangling like that permanently.
I had to Pre-order the new one
The old one works with pixel phones with a micro to C, I dont see why it would not work unofficially since hubs and other devices work from native C or micro to C. The only concern would be power draw.
The new CCGTV needs more power. 5V, 1.5A. The old one doesn't have enough amps.