I observed it on 18.04. It's hard to figure out the culprit - there is a concept of "seats" now, which ignore network logins. There is a concept of logind and login sessions. There is a concept of killing gettys and running them "on demand". There is kernel modesetting, wayland, etc. However, the virtual console was overtaken by systemd, logind, seats, and sessions have plenty open bugs, gettys are now some type of "service".
In the end - if you login as the same user - you're somewhere in "logind" + "session" + "seat" + "resource control", so exiting a getty might mean changes to login/session/seat/accounting, etc.
In my case I had additional usb(?) issues, as my mouse would no longer work, my keyboard was dead, but somehow the touchpad was ok. Or maybe there's something something with dbus on the way. We'll probably never know. My logs didn't say anything interesting, it was mostly:
"systemd did this, systemd did that, the result of the service is RESULT". Go figure. It didn't break in debian stretch yet, but with coming upgrades - who knows what's gonna happen.
Best Answer
Yes it is possible, depending on the laptop. Anything that uses the standard VGA text mod shouldn't have a problem with an external monitor, although you may need to switch on the external monitor using the keyboard switch. I had an HP laptop with a broken screen & was working with both the command line & X with an external monitor, without having the enable the screen when using a VT.