Minimum platform for iOS missing in Package.swift -> Does not compile

[GerdC]

I'm Switching from Cocoapods to Swift Package Manager in an iOS project.

I get many compiler errors similar to
'converted(to:)' is only available in iOS 10.0 or newer

The cause appears to be that Package.swift declares requirements for MacOS but not for iOS:

platforms: [ .macOS(.v10_12) ],

What is missing is something like

.iOS("10.0"),

PodSpec has the correct platform requirements:
s.ios.deployment_target = '10.0'
s.osx.deployment_target = '10.12'
s.swift_version = '5.0'