I figured out the issue: I was using the same series ID's between the two, even though there were separate. If I make sure they are unique it works.

I'm the same boat. I have a new Mac Studio Ultra but my iOS app's main dependency currently only builds for x86 for simulators. I can't seem to force all the SPM packages it relies on to build x86 simulator versions :( Apple really needs an Xcode setting to tell SPM how to build. It seems CocoaPods can do this https://blog.sudeium.com/2021/06/18/build-for-x86-simulator-on-apple-silicon-macs/