Getting the Apps must contain a provisioning profile in a file named embedded.mobileprovision error. I have added the "'args: '-UseModernBuildSystem=0'" even then facing the same issue.
      - task: InstallAppleCertificate@2
        inputs:
          certSecureFile: 'cert.p12'
          certPwd: '$(certpasswd)'
      - task: InstallAppleProvisioningProfile@1
        inputs:
          provisioningProfileLocation: 'secureFiles'
          provProfileSecureFile: 'app_profile.mobileprovision'
      - task: Xcode@5
        displayName: 'Xcode Development Release'
        inputs:
          actions: 'archive'
          sdk: '$(sdk)'
          scheme: '$(scheme)'
          xcWorkspacePath: '**/*.xcodeproj'
          exportOptions: 'specify'
          exportMethod: 'app-store'
          archivePath: '$(Build.SourcesDirectory)/build/iOSApp.xcarchive'
          exportPath: '$(Build.SourcesDirectory)/build/output'
          teamId: '$(TeamId)'
          exportTeamId: '$(ExportTeamId)'
          packageApp: true
          signingIdentity: '$(APPLE_CERTIFICATE_SIGNING_IDENTITY)'
          provisioningProfileUuid: '$(APPLE_PROV_PROFILE_UUID)'
          args: '-UseModernBuildSystem=0'
      
      - task: AppStoreRelease@1
        inputs:
          serviceEndpoint: '$(ServiceEndpoint)'
          appIdentifier: '$(AppIdentifier)'
          appType: 'iOS'
          releaseTrack: 'TestFlight'
          shouldSkipWaitingForProcessing: true
          shouldSkipSubmission: true
 
     
    