I spoke to an Apple Support tech via the support app on my iPad and through iMessage and brought the issue to their attention (by linking this forum post). I told them that by the looks of this forum it clearly is an iOS 18.5 issue that EVERYONE is experiencing. Hopefully this tech is able to forward it up the chain and it is taken seriously.
I’m also experiencing the mail app freeze on my iPhone 14 Pro Max. Mine specifically freezes when I tap on my Gmail folder, none of the others. I have 3 accounts linked - my iCloud which is a bundle consisting of of my .iCloud account and a few personal domains, Gmail, and an old Yahoo account. I’ll be checking mail or refreshing my mail to see if any new emails have come in and as soon as I tap on the Gmail folder to view the emails in it, it highlights the Gmail bar as I tap it, but nothing happens. Then the whole app is frozen and I have to reboot the phone.