You can put whatever in the initramfs, but since Linux just boots as a UEFI executable with CONFIG_EFI_STUB=y, it would be somewhat silly to start up a full use

You can put whatever in the initramfs, but since Linux just boots as a UEFI executable with CONFIG_EFI_STUB=y, it would be somewhat silly to start up a full userland via systemd in the bootloader. systemd-boot is a thing though, which is a pretty small UEFI application that reads a Freedesktop Boot Loader Specification config [1] from an EFI partition and tells UEFI to boot a kernel directly. Definitely no Linux or systemd-init involved though. [1]: https://www.freedesktop.org/wiki/Specifications/BootLoaderSpec/ https://www.freedesktop.org/wiki/Specifications/BootLoaderSp...