I know you say latest Edge but are you using Classic Edge or Chromium Edge? I think this can only be headless in chromium edge (but you could certainly try the headless option below).
You would be able to tell based on if you had sent in the chromium option: Open Browser | url | edge | options=use_chromium=True |
To make it headless it would be: Open Browser | url | edge | options=use_chromium=True;headless=True |
You will also need to be using selenium 4 or the plugin in the link below.
I wish I had an answer for you, I tried using edge chromium the first time the other week and couldn’t figure out how to get an “In Private” (incognito) window either, I looked at this thread and a bunch of threads about selenium with python and tried to create an options dictionary with python and pass that to robot so it could be passed in to the open browser. Nothing I tried worked for me otherwise I would have commented here earlier.
It is quite simple to run your tests in the headless mode. You need simply to add the “–headless” argument to the EdgeOptions object. NOTE: Make sure to download the correct version of Edge driver and copy it to the output folder. Also, you need to install the latest version of the Microsoft.