Get two-factor authentication code from terminal?
I came up with a pretty simple solution to this problem using AppleScript that should print the 2FA code:

#! /usr/bin/env osascript
tell application "System Events"
    if name of every process contains "FollowUpUI" then
        tell window 1 of process "FollowUpUI"
            click button "Allow"
            delay 2
            set code to value of static text 1 of group 1
            log (code)
            click button "Done"
        end tell
    else
        log ("Couldn't find 2FA window")
    end if
end tell
return

Adding this to a file and making it executable using chmod +x name_of_file.scpt should create a script that can be run over ssh by executing ./name_of_file.scpt while in the same directory as the file.

Note: When you run this script over ssh for the first time, the following popup should appear:



Simply clicking "OK" should allow the script to run properly. This preference will automatically be saved, and can be modified by going into System Preferences->Security &amp; Privacy->Privacy->Accessibility

This worked for me on macOS Mojave, but it may work on other versions as well.