Discovered accidentally whilst writing unit tests. Thanks for the explanation and advice.

Having the same issue. Building on devices is fine. MacBook Pro 15'' 2019 Xcode 12.5. On an iOS 14.5 simulator application is not able to make any network calls. Other iOS versions on the Simulators are fine. Error Domain=NSURLErrorDomain Code=-1200 "An SSL error has occurred and a secure connection to the server cannot be made." UserInfo={NSLocalizedRecoverySuggestion=Would you like to connect to the server anyway?, _kCFStreamErrorDomainKey=3, NSErrorPeerCertificateChainKey=(     "cert(0x7f9cb5020200) s: mobile-config.slyce.it i: GTS CA 1D2",     "cert(0x7f9cb5020a00) s: GTS CA 1D2 i: GlobalSign"