Ultrasonic cleaning sounds like a good method. For me I just remove the chain and soak it in a jar of Charcoal Lighter Fluid then re-lube and reinstall. Not to be disrespectful but lately I have come to consider chains as just another expendable item when worn dirty or not.
The old ChiCom Harbor Freight ultra sonic cleaner is good enough for chains and other parts. You might want to consider other alternatives for cleaning like you washing machine or dish washer...
https://www.bikeforums.net/bicycle-m...ur-washer.html