I misread the SE-0371 proposal at the time you posted. I see now it's a 'synchronous' deinit, so I don't see how it helps the situation of cleaning up with an asynchronous function. I tried it out yesterday in the release toolchain, and it didn't change the situation.

I’m able to see the exercises in the Fitness app along with their times, but the green ring doesn’t fill up.

Unfortunately when I try to kick off a new task, I get the error: … This object's deinit, or something called from it, may have created a strong reference to self which outlived deinit, resulting in a dangling reference.

Is this something that can be fixed in a future Xcode beta release, or will we have to install the latest MacOS beta? PreviewProvider produces a separate error 'Fatal Error in SchemaProperty.swift'.