Unfortunately it looks like this issue still exists. iCloud is selected as default keychain when opening the certificate. I tried @Najjii solutions and clicked on "always trust" but it didn't work. However, choosing "System" or "login" instead of "iCloud" worked for me. Thank you @Matt_SoundFingers & @dceddia. Is there any information why this does not work with iCloud Keychain? Any news about the bug report you've filed @DTS Engineer?

Similar issue here with the latest iOS 18 beta. For us, the principal placement causes the tab bar to increase, while looking good with previous iOS versions.