Alright, we found a solution. Finally haha. You need to get the Apple Distribution certificate and create an App Store provising profile within: https://developer.apple.com/account/resources/certificates/list (Certificates, Identifiers & Profiles) if you haven't already. Then in XCode you go "Product" -> "Edit Scheme" -> "Archive" change it from debug to release and then archive your project with your app distribution profile you created. The app will crash if you compile your app directly from xcode using your app distribution profile and it will also crash if you use your apple development profile to App Store/Test Flight. When compiling use Apple Development Profile when archiving in RELEASE mode use Apple Distribution Profile.

Update: It's most likely have something to do with certificates. We were having an development profile. Within https://developer.apple.com/account/resources/profiles/list Certificates, Identifiers & Profiles -> Profiles add a new one for "Distribution" -> "App Store Connect". I am going home from now but will keep working tomorrow on the problem and hopefully find a solution tomorrow :)

We can see that it crashes now. We put the app on testflight and it does crash on start up. We can still not see any errors regarding it. There is something between compiling release mode directly from xcode to physical phone and then distributing the app. I guess it's a good start - now we have a way to do some changes and test it instead of waiting for an app review everytime. I will keep you updated if I find any solution :)

Yea, these crash logs was from our previous build (we assume it is the same error happening), the newest one didnt have any crash logs either.. Hopefully someone here in the community can help. I wrote to Apple Review team and will give the answer here once I get it