The i386 architecture is burdened by outdated compatibility features that are no longer necessary. These features hinder the development of new software. The i386 boot process, designed for floppy disk drives and limited firmware, remains unchanged and makes certain tasks, such as configuring multiple operating systems on a single machine, complex. The Extensible Firmware Interface (EFI) provides a more versatile boot process for Intel-based machines, but the i386 architecture will still continue to be used for a long time. The Multiboot Specification aims to resolve some of the limitations of the i386 architecture through software, allowing any operating system to be booted from a single boot loader. The NetBSD kernel has been modified to become Multiboot-compliant. The Multiboot Specification defines a protocol between boot loaders and OS kernels, allowing any Multiboot-compliant boot loader to load and execute a Multiboot-compliant OS kernel. By making the NetBSD kernel Multiboot-compliant, users can easily dual-boot Linux and NetBSD. Adapting other operating systems to this protocol could be a next step in further improving boot processes.
https://jmmv.dev/2007/03/making-netbsd-multiboot-compatible.html