I'm also a bit disappointed due to the lack of SE05X support.
There is a built-in secure element with tons of functions available in the datasheet. And ... on the Arduino ... nothing. There are some functions for the cheap Portenta C33 but I cant understand why this is not included in a 200+€ product
In order to make relevant information available to any who are interested in this subject, I'll share a link to the formal report @jowin202 submitted to the developers of the "Arduino Mbed OS Portenta Boards" platform: