Ok, so I have found a workaround to this. It's all described in this tweet: twitter.com/SawyerBlatz/status/1290824315223420930 The only difference from the tweet that was mentioned by shoji_bf is that you also need to uncheck "Include bitcode for iOS content" when uploading your archive, and the widget is finally there! Hopefully it's going to stay there and all of this stuff is going to be fixed before the release. I'm going to submit that binary to external testing review, see if Apple will find the widget in the gallery too.

I'm glad I'm not the only one in this. I have found another crash that has been reported through TestFlight lately: WidgetKit: specialized closure #2 in WidgetExtensionContext.getTimeline(for:into:environment:isPreview:completion:) + 1332. I don't know if it's related or not, but I better leave it here. It has been reported several times already along with WidgetKit: closure #1 in WidgetExtensionContext.getDescriptors(completion:) + 176 in the same build.

Thank you shoji_bf for mentioning that tweet. I did what that person recommended, but unfortunately it didn’t help. Then I also switched off Dead Code Stripping for my Intents extension, that had no effect either. I even tried to switch it off for the whole project, but also had no luck here. Meanwhile I fixed my CFBundleVersion mismatch error as well as other Siri support errors that I was having when uploading builds to TestFlight. Still no widget 😔 It’s so strange, because I can see my widget when running the app through Xcode in Release configuration. I also see error No intent in timeline(for:with:completion:) when debugging my widget, although it successfully launches. And the method name is old in this error, too, I don’t use it anymore.

I have noticed that I received a few crashes on TestFlight from my own device: WidgetKit: closure #1 in WidgetExtensionContext.getDescriptors(completion:) + 176. Unfortunately, it doesn't say anything more than that. Then only link Google finds is https://developer.apple.com/forums/thread/655776 and the solution doesn't apply to us, because all widgets must be rebuilt using the beta 4 SDK. I have also tried to remove the widget extension target and its code completely and create it again — but this had no effect at all.

I wish there was a way to set unit flags for this custom Text initialiser. Without that the way I present data in the app will be different from the way I present data in the widget which is kinda bad for users. Anyway, thank you for your answer!