The other possibility is that you could have Ekos display just the star profile image, which PHD2 is always sending with the guide data no matter whether the camera is only connected to PHD2 or if it is an INDI camera. The method I always use is to get just the star profile image and I know that method is working because I use it all the time. If the other method no longer works for some reason, let me know and I will look into it.
My belief is that the option to receive just the star profile image is far superior to receiving the whole external guide frame. If you have the camera connected to INDI and it has to send images across the wifi network, that really slows down response time for guiding. It is much better to set up your INDI profile to leave out the Guide camera if it is natively supported by PHD2, then directly connect your camera to PHD2, and connect to PHD2 from Ekos. This won't hurt the control of the camera because PHD2 is the one doing the guiding and you can control most of the important functions from Ekos. The star profile image and all guiding data will come back to Ekos, and while the star profile image isn't that big, it is definitely good enough to see the star PHD2 is using for guiding and to see that there are no problems with the guider. As I said, I know this is working perfectly still because I was just using it last night and I have it running right now in the simulators with no issues.