You can test out plate solving with an existing image. On the Solver tab, click on Load & Slew and pick a light frame you've shot recently. I tested it with Ekos running the Simulator profile so it wouldn't slew my scope after solving.
Lin_guider is another linux-based guiding application. I've never used it.
I stumbled across this guy's videos: https://www.youtube....jurgenko/videos Look for the ones labeled "Live Astrophotography". He actually recorded a couple of full night imaging sessions using Ekos! They are very long, so waaaay too much to look thru all of them, but I did find them fascinating to watch as he was setting things up and working thru the various functions of Ekos. He seems to favor the internal guider, so you might be able to pick up some tips there.