OK, I figured it out. the key to getting CLKComplications working on a single target watch app is to implement the getComplicationDescriptors(handler:) method in your ComplicationController class. I had the Complication Families specified in the info.plist file which doesn't work in watchOS 7, and that key must be deleted from info.plist once the new method is added.

Thank you for figuring this out. I've had the exact same issue as the topic starter, and migrating to a single WatchKit target fixed it! Just like in your case, migration wasn't exactly smooth, but still much better than having to rework the whole app into SwiftUI. I can confirm that my ClockKit complications are broken too now, and I'm trying to figure out what's going on there. I can add them to my watch faces just fine, but they never update and just keep showing the preview name.

Thank you. Too bad to hear, but if it's at least technically possible I can give it a try. The thing I was thinking of doing is more of a hobbyist rather simple free game, so I can't really justify any extra cost.