https://www.rodsbooks.com/refind/getting.html

unzip to flash drive

rEFInd: How to Install and Boot Alternative OS on Mac

after install /boot/efi/EFI

refind.conf to change boot

https://askubuntu.com/questions/348463/refind-configuration-change-boot-order-and-default-boot

default_selection "UBUNTU\EFI"