Download current and previous versions of Apple's iOS, iPadOS, watchOS, tvOS, audioOS and macOS firmware and receive notifications when new firmwares are released.
You can still restore to 13.7 as it is still being signed, but you have to download it and select it during the restore process. Start here: https://ipsw.me/#
I appreciate the advice. Unfortunately I'm unable to get Finder to see my iPhone 11. I did turn that on in the Finder preferences (actually it was already on).
Is it possible to store that iPSW and use it at any time or does it stop to work as soon as Apple has stopped to sign it?
(I don't dare to upgrade to iOS 14 on my old iP6s, since I once made the experience, that the last possible iOS Update rendered my 1st gen iPad-mini close to beeing useless - speedwise)
Update/downgrade to any version is only possible as long as apple is signing it. Therefore as soon as apple stops to sign iOS 13.7 you can no longer downgrade.
I attempted this as I want to go back to iOS 13. However, I did download the signed iPhone Pro Max version and it does not work - I always get image not authorized.