How do I get display resolution on modern macOS?
Here's an answer. Warning: in addition to my solution, I've captured other solutions from the comments above.

I used this from the commandline:

system_profiler SPDisplaysDataType | grep Resolution

The other answers worth trying are:


Find it via the "About This Mac" in the system report (@nohillside's answer)
System Preferences > Displays > Display. Then click the "Scaled" radio button and it will display the current resolution and allow you to change it. If you don't want to change it just click back to "Default for display" (Steve Chambers' answer)
open the "About my Mac" and click on the display "tab" that is second from the left. The resolution is shown there (me) 


All of these work fine.