Finder not showing latest iOS update

macOS on Sequoia 15.3.2, iPhone 13 mini on iOS 17.7.2,

iOS 18.3.2 out since days (and earlier 18.3 since a while)

Want to update iOS on iPhone using Finder on Mac:

iPhone is visible in Finder, click on "Check for update"

gives

"This version of the iPhone software (17.7.2) is the current version."

Any idea what to do to get it working?

iPhone has plenty of storage space, that cannot be the problem.