So . . . just to make things more interesting (and somewhat confusing) . . .
T-Mobile in the US has decided to leave it's 2G service up for now (although, it is my understanding that the 2G coverage area has been slowly shrinking and will eventually be shutdown).
I placed my SIM inside my Nexus 5 and was shocked that I could still make calls (which sent me to dive deeper and find out why).
At some point I will test how reliable using 2G for calls is (my guess is urban areas have somewhat reliable coverage, but rural coverage will be horrible [based on what I remember the service was like back in the day]).
I might even re-install UT on my Pixel 2XL (my daily driver).