Raspberry Pi - TV Signal not found. Video signal lost. Also, "Switching audio to TV speakers"
During a long software update or software installation, the video signal is lost. Switching the TV's input, from [hdmi 1 to hdmi 2, etc.,] did not help.
Issue:
I had the Raspberry Pi connected to the home TV, which was patched through a home stereo. The stereo receiver would get bored and would power-down (energy savings).
Powering on the stereo receiver restored the Pi's video.
Related article:
Raspberry Pi - Installing network-wide ad-blocking with Pi-Hole.
