I'm finding that when I plug and unplug my monitor, into my laptop it doesn't restore a proper view or workspace, it just shows a blank screen. I can mouse around that screen and between screens, but it stays blank.

(defun cc/build-workspaces (l n)
  (cons
   (cons n (car l))
   (if (cdr l)
       (cc/build-workspaces (cdr l) (+ n 1))
     nil)))

(defun cc/exwm-randr-screen-change ()
  (setq cc/screen-list (process-lines "sh" "-c" "xrandr | sed -n  's:\\([^ ]\\) connected .*:\\1:p'"))
  (setq exwm-randr-workspace-monitor-alist (cc/build-workspaces cc/screen-list 0))
  (setq exwm-workspace-number (+ 1 (car (car (last exwm-randr-workspace-monitor-alist)))))
  (setq exwm-randr-workspace-monitor-plist (list-utils-flatten exwm-randr-workspace-monitor-alist))
  (let ((first (car cc/screen-list))
	(rest (cdr cc/screen-list)))
    (dolist (screen rest)
      (start-process-shell-command "xrandr" nil (format "xrandr --output %s --left-of %s --auto" screen first)))))

(add-hook 'exwm-randr-screen-change-hook #'cc/exwm-randr-screen-change)

Which seems to work. Every time I plug in my monitor and check the value of exwm-randr-workspace-monitor-plist it looks correct, which is (0 "eDP-1" 1 "DP-1") when it's plugged in, and (0 "eDP-1) when it's not plugged in.

But here is the odd thing, I've got s-0 - s-9 keys assigned to switch workspaces:

(setq exwm-input-global-keys
      `( ,@(mapcar (lambda (i)
                    `(,(kbd (format "s-%d" i)) .
                      (lambda ()
                        (interactive)
                        (exwm-workspace-switch-create ,i))))
                  (number-sequence 0 9))))

I find that if I flip workspace to one I didn't use before, say workspace 2, suddenly boom, my monitor starts showing what it is supposed to, as if it kicked it into reevaluating. That's despite that the monitor shows workspace 1 always, and s-1 still takes me to the monitor, not the new workspace. All these new workspaces still belong to my laptop screen, not the monitor.

But the thing is, every time I unplug and plug I've got to use a higher workspace number. The next time s-2 won't work, I'll have to go to s-4 or something. Eventually I run out of workspaces 0-9, and have to resort to manually creating them with (exwm-workspace-switch-create some-big-number) to get my screen working again.