So, I may have been living under a rock, but I just recently realized that actual UEFI bootloaders exist for the Raspberry Pi 3 & 4! That's exciting - I was never really a fan of ready-made images, and here I am GRUB-booting vanilla Debian testing on my Pi 3!

Info for my rock-dwelling comrades:

https://www.raspberrypi.org/forums/viewtopic.php?p=1730396

https://pete.akeo.ie/2019/07/installing-debian-arm64-on-raspberry-pi.html?m=1