Hello
While trying to federate Configuring Workflow Manager Server with an ArcGIS Enterprise portal it is mentioned in the ESRI documentation that You must connect to theArcGIS Enterpriseportal through theArcGIS Web AdaptorURL. Please find below screenshot for your reference.

More info here
I have tried passing server url along with port name while federating and found that it does not accept and says invalid url.
I was thinking if there is any other way out. If anyone has tried without webadaptor url.
Please share your thoughts on this.