I have new Q70R 65".
I connected to google home,through the smartthings app.
Home can't find the TV otherwise.
I can cast YouTube to the Q70R or to my chromecast on another TV.
I can cast google photos only to the chromecast, but not the Q70R.
This doesn't seem right.
How can I cast photos form my android phone to the TV?
Have you tried to download Smart Home? That might help.
I have exactly the same issue. Q75R 55".
The TV only appears in the 'Cast' menu options on my phone (Galaxy S9) when I use the YouTube app. I notice that it appears with "[TV] .." prefixed to the TV's cast name.
All other apps that support 'cast' don't list the TV as a cast option.
I'm guessing that Samsung haven't implemented a full Chromecast functionality in these TVs (despite what the advertising leads you to believe). It appears to be a locked-down cast solution that only works in conjunction with 'SmartThings'.
For me this renders the built-in 'cast' useless. I can't cast from Photos. I can't cast from VLC. I can't cast from any of my phone's TV catch-up apps (e.g. ABC iView here in Australia).
I was hoping with this new TV I could ditch the old Chromecast dongle, but I have it plugged back in now, and it's working as it should.