That did the trick, thanks! Weird that the error details would talk about code signing when the problem was a missing runtime, but go figure.

I've switched over to using Lunar as of this morning, following the runtime install. Unfortunately, it looks like today's going to be cloudy straight through, so I don't know that I'll get the best opportunity to see the app strut its stuff right away. That said, the UX has been very solid thus far, and I like the extensive configurability even if I have no intention of using more than about 5% of it.

Strong recommend, and definitely worth a coffee!