For anyone interested, I can confirm that the new Chromecasts with a remote and Android TV work with CATT, and I also managed to sideload the Home Assistant app and Fully Kiosk browser.
Also plays well with browser_mod.navigate.
The remote is a little limited for navigation of some apps, but you can fill in some of the blanks by installing a remote app on the device and your phone and then have a pointer mouse etc.
Haven’t used extensively yet so not sure what might be lurking …
How did you sideload the apps?
You basically just need to find the .apk for the app online and get the file onto the chromecast, then just open it to prompt the install.
For example, from the Play store on the Chromecast, you can install Downloader by AFTVnews.com then browse to a webpage where you can download the .apk.
Alternatively, you could install a file browser like Solid Explorer that will allow you to add a network location where the .apk is (like your PC or rasp pi).
You’ll need to change a few security settings for installing apps (maybe in developer area or security in Chromecast settings, I forget)
Thanks for the idea ! I managed to install the apps but could not find a good app which allows remote input… I could not get pass the HA authentication page
Try Android Box Remote app. Works for me.
Not sure I’m downloading the right one, but the one I found (Android TV Box Remote) is for devices which has an infrared sensor…
That’s ok, thank you ! 
Just figured out that if you have CEC on your TV you can both turn on/off the TV/Chromecast and even open apps via the Google Assisstant Webserver (have tested with Fully Kiosk Browser and Homwe Assistant). That’s nice!
in config:
notify:
- name: Google Assistant
platform: rest
resource: http://192.168.1.xxx:5000/broadcast_message
- name: Google Assistant Command
platform: rest
resource: http://192.168.1.xxx:5000/command
in script:
tv_on:
sequence:
- service: notify.google_assistant_command
data_template:
message: open Fully kiosk browser app on Living Room TV