A small set-top box (essentially a Steam Deck with the screen, controls and batteries removed, and with components that don’t have the space restrictions that come with a mobile device) would still be an interesting proposition. Particularly if they partnered with the main video streaming services to port their apps across, and implemented Chromecast/AirPlay support.
I can see a market for it, as a “Chromecast and Apple TV competitor that also plays all your games”.
The UK isn’t quite that far, but it’s absolutely the dominant text messaging and calling app in the UK. Nobody uses the built in Android or Apple tools anymore, and I’m as likely to receive a WhatsApp voice call as an actual phone call these days.
I have Signal on my phone, but I’ve literally never had a cause to use it; I’ve simply got no contacts on there.