Thanks for the post and the details, the error is not about having the latest version of Xcode, looks like you do have it as Xcode Version 26.2 (17C52). The error message you're encountering, ITMS-90426: Invalid Swift Support - The SwiftSupport folder is missing., indicates that your app submission to App Store Connect is missing a required folder named SwiftSupport.
So this is extremely interesting to me for sure. When archiving your app, ensure there are no build warnings about folders. Go to > , and then check the Organizer to ensure everything is correctly packaged. If your app uses Swift Package Manager, ensure that all packages are updated and correctly integrated. Sometimes issues arise from improperly configured packages? I believe this issue is always about packages you are using. Can you check that? read until the end where a post from an Apple engineer will give you more information. If you're manually managing your app bundle, ensure the folder is present in the archive's structure. It should be located at the root level alongside your file. Normally, Xcode handles this automatically.
I am not interested in how you build your Objective-C and Swift together and set up the bridge header. Did you let Xcode do it for you?
I do not believe this is a bug and I believe you have submitted one today? I think this is a configuration issue on your project that is preventing the SwiftSupport build from being created.
My personal recommendation at this point is to create a new project in Xcode and add some Objective-C code and let the bridge header be created. Then when submitting, you will not receive this error and you can compare the differences between both projects instead of trying to find out the issue looking at how the project was setup.
But I never seen this issue but we have people that has and some post about it, hope someone here have seen it previously and realize what setting is causing the SwiftSupport folder to be excluded normally is a library and external framework from the post below:
We have a post from an Apple Engineer about this here that will provide most of the information https://developer.apple.com/forums/thread/765288?answerId=807098022#807098022
Albert Pascual
Worldwide Developer Relations.