Welcome to Lightroom Forums Ron!
You are talking about two unrelated things here: Monitor profiles vs Printer profiles.
Where do you see "Color managed by Lightroom"? The closest thing to this I can think of is in the Print module where, under color management, you can choose between "Managed by Printer" or "Other...". In this case, we talk about print profiles.
Lightroom always use the monitor profile you set in your operating system. The recommendation is to create a monitor profile yourself as those coming with the monitors are generally of bad quality. The
white point, gamma, intensity, & contrast ratio will be set and or suggested by the software that come with a device you have to buy separately such as a colorimeter or better yet, a spectrophotometer. Expect from 2''$ for lower end products to many thousands for high end industrial products. I have found
a very nice, effective and extremely complete solution at 4''$.