Question on HDMI external display behavior

[michaelryan55]

I have generally only used wireless solutions for my second monitor in the home office, but lately I got a bit aggravated with using an Apple TV or Sidecar, and decided to use a USB-C to multi-port adapter on my 2017 MacBook Pro. However, there's something I haven't quite figured out or I am doing wrong... or is this just normal function at this time?

Here are my steps when returning after using the MacBook Pro away from my desk:

1. MacBook Pro is powered off and clamshell closed
2. Plug in USB-C to multiport adapter that has USB-C power and HDMI both connected already
3. MacBook Pro turns on automatically since that's what happens on newer models when power is connected
4. It immediately pops up login screen on external monitor (but I don't have external keyboard and mouse connected often)
5. If I open the clamshell the screen is black, external monitor also black
6. This also happens when coming back after the computer is locked, even with the clamshell open. I briefly see the login screen but then it goes to black.

Any way around this? I can still type in my password, hit enter, and have the computer boot -- but I don't see the log in screen and always worry that I screwed something up...