What is it about the MLS encryption that is dubious?

What weak link?

MLS is cool because ANY messenger can implement it and talk to another messenger. If implemented, Signal users could have an EE2E conversation with WhatsApp, or Matrix users could have EE2E conversations with RCS users.

The original creator of MLS has a messenger called Wire.

And technically the key file can just be a plain text password and still work. Just as long as the key file matches the drive’s encryption password.

If its encrypted, you can also decrypt the drive automatically once booted by adding an entry in /etc/crypttab

This will make it so you don’t have to type the password.