I have filed several feedback reports on this going all the way back to iPadOS 16: FB14461493, FB12041189, and FB11724692 at least. One requested the actual certificate rather than the text listing from OpenSSL. None have been closed. My experience is that if the device can run iPadOS 15 or less, there isn’t a problem with trusting the root cert. if it was installed in iPadOS15 or earlier and trusted, it will stay trusted even if the certificate is updated, through upgrades up to iPadOS 18.1. Unfortunately, that’s not a viable solution if you’re a device to new to do the old install (M2 and later). Often, the certificates will give an error message, but not give you any option to even trust the certificate signed by the self-signed root. Other times it eventually “just works” and stops complaining. But not always. The most persistent problem I have is with an imap server. Today it seemed at least on a test teablet (which does have the cert installed and trusted). The pop client worked whereas the imap client has chronically failed even with the trusted root. I then upgrade my regular muchane running iPadOS 17 with the imap server (but not with the root installed as it’s an M2 that could never ru pre-iPadOS16), and the unap server still fails. I will try switching to the pop server To see if that works. Both servers run on the same machine, so cers are really all the same.