Wow! Thanks for the thoughtful replies luxonis-Sachin and Brandon!
I should have provided test images and even code, but I had hoped there was something obvious I was doing wrong. I have played with tuning HoughLinesP (and other functions), but have not seen much, if any, improvement.
I am not familiar with corrosion or erosion filters, but will certainly do some investigation and experimentation. In the long run, ROS is on my list of topics to at least investigate, but it is such a different beast that I'd have to redo most of my current environment, and I'm not at a point where I'm willing to do that.
As far as my plans for indoor navigation, I really don't have firm plans. I was successful (mostly) in using a simple, but pretty accurate, LIDAR unit to facilitate localization and navigation, and I'm trying to find how best to use the OAK-D to replace it. So, sadly, I can't answer how I would classify items, because I simply don't yet have enough knowledge to do so.
I have a time-critical task in a very different area that will keep me busy for roughly a week. After that, I'll return to this topic and I hope to be a bit more specific with questions and answers.