Here's a real answer that these moderators just aren't capable of:
I've been experiencing it too on Q60 65". Starts off as external device via H/K AVR then disappears. I can get it to display by turning on firestick with firestick remote (since firestick supports Anynet+ CNC), and when I do the recent tile in the smart hub home still calls it the correct thing (H/K AVR). This means it's there but for some reason the source visually disappears from choice. Further confirmed by the fact that my TV remote can still control the firestick too via Anynet+ CNC.
I did try unplugging hdmi between TV and AVR then unpowered, repowered, gave the TV a minute to fully boot then reconnected hdmi and that fixes it... for about a couple days and then the problem is back. Definitely a glitch in the code. Too bad our problems will fall on deaf ears because Samsung community moderators are as useful as a bot and Samsung as a company is terrible at collecting VoC (voice of customer) so devs will probably not notice...
If any member of significant authority from management actually reads this, you might want to woo me as a director of product management or equivalent... as a director of continuous improvement with a lean six sigma master black belt and global experience deploying enterprise tools, I can fix you guys up quick... a lot things I would change about company practices...
