REFInd
rEFInd is a boot menu and maintenance toolkit for UEFI-based machines. It can be used to boot multiple operating systems that are installed on a single non-volatile device. It also provides a way to enter and explore the EFI pre-boot environment using an interactive shell, for example shellx64_v2.efi.
rEFInd is the active fork of the now-abandoned rEFIt and the default Unified Extensible Firmware Interface boot manager for TrueOS.
The popular Manjaro installer "Architect" also adopted rEFInd by 2018.
GNUefi lends itself to writing binary efi-applications in C to launch right from the rEFInd GUI menu. Typical purposes of an EFI-application are fixing boot problems and programmatically modifying settings, which would otherwise be performed from within the firmware-BIOS of a personal computer.
