I’ve had both a Gen2 and Gen4 doorbell and both have worked with my current wiring.  I just purchased a 4k Gen3 and got a red flashing light which indicates my wiring does not provide enough power.  I ordered a newhouse hardware 24v 40va doorbell transformer.  But after looking around i have no clue if i have one already or even where it would located.  Possibly in the Attic.

But i got to thinking it has a USB-c and the installation is in a good spot i could mount a solar panel to provide power.  But the solar panels don’t say they are compatible with the wired doorbell pro Gen 3.  Is this correct?  If so, what is the USB-C used for?