2017Ridgeline emergency horn & ignition switch issue.
 

Recently found a direct relation with this issue and emergency horn going off randomly.
The dash lights flickering and fuse box relays clattering sometimes goes on for a minute or two.
Any thoughts or solutions appreciated, thank you.

welcome to the forum. Dirty battery terminals and poor ground attach, or Weak battery, will not hold a full charge. Check the battery by doing a load test, auto parts places do load test. Also poor fire wall connections can cause this also.

New battery & ignition switch and 3 appointments with Honda service tech.
Service tech says, We don't know if it's not doing it...
My question,'Why is there no code(s) stored as to why horn was activated? This has happened lots of times in the last 3-4mo. The neighbors are getting restless.

No codes stored due to no sensors in that system to tell the computer(s) there is a fault.
Not everything is hooked up with sensors and there is a limit to how much the computer can handle??
So ECU handles engine and related components
Body Control Module (BCM) handles body related issues
ie, doors and interior lights, horn, etc.,
Your code reader might not read that module??
In some cars, there are up to 18 different modules.
And most codes only point to an issue and not why someone thing went wrong.

Note: You said you found a direct relation with this issue??
What was the relation?

Not direct relation, still guessing why, what, when, what if,...
I recently became aware of a faulty ignition switch issue with my model. My impression is, it was replaced with another faulty switch.
Again, while parked in the driveway with windows down and key fob in the car, I could hear relays clattering as if the ignition switch were being pressed once every 2sec. along with dash fault indicators flickering. This lasted for 10-15 seconds.
This has to wear on the mechanical/electronic components.