I don’t get it? They seem to be arguing in favor of bootc over systemd because bootc supports both split /usr and /usr merge? But systemd is the same. There is really nothing in systemd that requires it one way or another even in the linked post about systemd it says:
Note that this page discusses a topic that is actually independent of systemd. systemd supports both systems with split and with merged /usr, and the /usr merge also makes sense for systemd-less systems.
I don’t really get his points for it either. Basically boils down to they don’t like mutable root filesystem becuase the symlinks are so load bearing… but most distros before use merge had writable /bin anyway and nothing is stopping you from mounting the root fs as read-only in a usr merge distro.
And their main argument /opt and similar don’t follow /usr merge as well as things like docker. But /opt is just a dumping ground for things that don’t fir the file hierarchy and docker containers you can do what you want - like any package really nothing needs to follow the unix filesystem hierarchy. I don’t get what any of that has to do with bootc nor /usr merge at all.
This isn’t true? The Linux kernel has a lot of drivers in the kernel source tree. But not all of them. Notably NVIDIA drivers have not been included before. And even for the included drivers they may or may not be compiled into the kernel. They can and generally are compiled with the kernel but as separate libraries that are loaded at runtime. These days few drivers are compiled in and most are dynamically loaded depending on what hardware is present on the system. Distros can opt to split these drives up into different packages that you may or may not have installed - which is common for less common hardware.
Though with the way most distros ship drivers they don’t tend to spontaneously stop working. Well, with the exception of Arch Linux which deletes the old kernel and modules during an upgrade which means the current running kernel cannot find its drivers and stops dynamically loading them - which often results in hotplug devices like USB to stop working if you try to plug them in again after the drivers get unloaded (and need a reboot to fix as that boots into the latest kernel that has its drivers present).