I am encountering linking errors when building macOS 11 apps/frameworks which use the Lightstreamer dynamic libraries. The exact error I get in the Xcode 12.2 build is:

ld: warning: ignoring file /Users/.../Library/Developer/Xcode/DerivedData/.../Build/Products/Release/Lightstreamer_macOS_Client.framework/Lightstreamer_macOS_Client, building for macOS-arm64 but attempting to link with file built for macOS-x86_64
Undefined symbols for architecture arm64:
"_OBJC_CLASS_$_LSLightstreamerClient", referenced from:
objc-class-ref in StreamerLowlevelTests.o
objc-class-ref in IG.o
"_OBJC_CLASS_$_LSSubscription", referenced from:
objc-class-ref in StreamerLowlevelTests.o
objc-class-ref in IG.o

The error references some of my test files, but if I understand it correctly, Xcode cannot link to the binary framework due to incompatibilities between the app architecture (arm64) and the dynamic library architecture (x86_64).

I am trying to find solutions by tweaking my Swift Package Manifest and using Rosetta 2 for emulation. So far I am unsuccessful, but I am trying to contact people on the Swift forums. I will post any solution I find here. It would save me a lot of pain, though; if Lightstreamer would just release their dynamic libraries with both x86_64 and arm64 as fat binaries. Lightstreamer already does this with iOS and tvOS, so I don't think it would be much more than a recompile with the new Xcode toolchain from your side.