Ok it’s fixed now. If you force quit the app, then open it and wait a few seconds (or enough time for it to download the 2MB update in the background) then force close it and restart it, it should work again. If that’s still not doing it, reinstalling the app should fix it.
Sorry about that! iOS 15 somehow broke an old web feature and was crashing, but only on the old version of the app built with the old version of Xcode (Apple developer tools). So all the recent work I’ve been doing with the latest versions of the tools showed no problems. That was super annoying to track down…