So there is no such thing as relays on your vehicle? That is what I meant by switches - relays adjust the current flow between on/off buttons on the dashboard and whatever battery they end up drawing power from.
My guess is that both the climate control on/off switch and the ESS on/off switch are connected to the AUX battery which is not getting enough juice from the MAIN battery to permit big power drains to switch on. Seems to all go back to underpowered MAIN batteries that develop bad cells much...
After reading or at least scanning hundreds of postings with these similar complaints I have found your solution of just replacing the batteries, in spite of their young age and regardless what redundant testing equipment says, this is the ONLY one reported by most people as THE ultimate fix.
In my opinion the "plain jane electronics" and the "garage cover" make an immense difference in security of the battery and all other electronic/digital components on any vehicle. Mine is a 2018 full of these modern electronic engineering nightmares and it sleeps outside in the wicked winter...
Sounds like you're just one of the lucky members of hopefully a majority. Like in everything else, people tend to post their problems not their lack of problems on these forums. After enough such negative accumulation the herd message begins to look like we are all screwed! Count your blessings...
I'm thinking of just changing the main battery then watch and see. Anything wrong with that, other than finding out later that aux also needs changing?
So there is no resetting of the on board computer or such required? just remove both cable clamps and re-hook all disconnected cables onto new battery? I am supposing the cable from MAIN to AUX must on the positive post of the main...
Since the AUX apparently gets its juice directly from the MAIN battery, it would make sense to replace the MAIN first. I just tried your instructions and sure enough my MAIN shows 12.4 with key in run position but motor not started. When motor starts, same info menu selection jumps to 14.4...