For instance, initrd is not verified: >>36717975
>The page you link goes into custom secure boot keys, which are usually unnecessary.
You might be right about that.
To use secure boot without calls to mokutil and friends, Unified Kernel Images are introduced in Fedora 38. These images contain everything (kernel, initrd, and so on) in one, published package. If https://bugzilla.redhat.com/show_bug.cgi?id=2159490 is to be believed, UKIs are live already in Fedora 38.
I can only find pregenerated UKIs for virtual machines in the Fedora repositories and I can't tell if they're properly signed or not, but support is being extended and this problem is being solved.
As for providing security: Linux really needs an easy, user-friendly GUI application for setting up proper secure boot. Of course at least one step is out of the control of Linux developers (configuring the firmware to load new keys) but right now "I want to load my system keys (and also the keys for my Linux dual boot)" is awful on any Linux distro. Every guide presents scripts to call scripts to call automated tools but none of them seem to make the process any easier or friendlier.
In my search I focused on the "immutable" distros like Silverblue because it seems to me that the immutability would make the implementation easier.
In contrast, all the other mainstream OSes can detect an alteration in something like the C library during boot.