https://wccftech.com/apple-is-no-longer-signing-ios-13-4-1-jailbreakers-need-not-worry/

Apple has just stopped signing the iOS 13.4.1 and iPadOS 13.4.1 firmware for both iPhone and iPad, blocking all downgrades from iOS 13.5 / iPadOS 13.5.

iOS 13.5 and iPadOS 13.5 was released little over a week back and Apple has been sining the iOS 13.4.1 and iPadOS 13.4.1 firmware alongside it. What this means is you could downgrade from the newer firmware to the older one, or bypass the 13.5 altogether and just upgrade to 13.4.1 if you wanted to.