> Apple does sign the entire boot process but they have the benefit of a strictly defined hardware set to support Windows can also sign the entire boot process

> Apple does sign the entire boot process but they have the benefit of a strictly defined hardware set to support Windows can also sign the entire boot process, but they unlike Apple can't make the system folders read-only due to backwards compatability (Windows 10S experimented with this idea but was scrapped). There's nothing stopping Linux distros from having a secure boot process, but the initramfs either has to be scrapped or pre-built by the distro.