Hi @cforsmark.
You should be able to follow the same procedure as I described in post #12 on macOS. I just personally verified that it works fine on my macOS machine with an UNO derivative board that has the CH340 USB to serial bridge chip.
Please try performing that procedure on your macOS machine and then let me know if you have any problems. If so, please tell me at which step the results were not as I described. Also tell me which browser you are using (e.g., "Safari", "Chrome").