Design language

" it's quite possible the Mac app will use Swift UI again at some point when we don't have to worry about that choice cutting off a sizable share of macOS versions."

Why not make that cut with 1P8? You're going to have to keep 1P7 under maintenance because of the anti-electron customers (or lose them). There are lots of apps that no longer work with things older that Catalina, and many not even that. So make 1P8 the go-forward, native app, and let legacy users ride 1p7 into the sunset until they upgrade to a modern supported OS. That's 2-3 years (because older than that even Apple doesn't support).