Have you tried logging into the following Hue website to see all of the Hue bridge integrations? It can be a little eye opening.
I know the Amazon Echo devices can locally connect to a Hue bridge, without using any sort of Alexa Skill. I believe Logitech Harmony hubs do the exact same, as well as Home Assistant, etc... If you log into the above site, you can drill down to see all of the devices that can control your Hue bridge. It might then become obvious.
Did that a couple of days ago now and I found two more apps that I forgot about. One of then must hav been the bad guy because it seems that the problem is gone now since I removed access for those apps.
