This reply isn't going to be helpful to OP, but thought I might add context for others passing by.
I'm using Arch Linux with LUKS encryption and gdm. As long as my user's password is the same as the LUKS password, I only ever type my password in once.
Just saying that a MacOS-like convenience is definitely possible on Linux.
Oof - forgot to mention that I do have autologin configured on gdm ๐