I upgraded Xcode from 12.2 to Xcode 12.3 and after upgrading, the build fails on the ArcGis framework with this message:
"Building for iOS Simulator, but the linked and embedded framework 'ArcGIS.framework' was built for iOS + iOS Simulator."
Here's a Stackoverflow thread on the issue (not ArcGIS specific though):
Also, you might want to consider distributing XCFramework files to be able to support multiple architectures properly.
Just to follow up on this, ArcGIS Runtime 100.10 (update 10) was released last month. It uses the XCFramework format and works well with Xcode 12.3.