Just checked and amusingly I'd forgotten that boot/root predated LILO, I must've first seen LILO when I installed Softlanding Linux.
Since I didn't have any networking on my home machine, Linux was basically a "Look, run GCC on your home machine!" option for '91 that didn't involve going through DJGPP's DOS port.
https://yosemitefoothills.com/LinuxBoot/BD-1Disk.htm
Here's some more documentation on this: https://www.kernel.org/doc/Documentation/x86/boot.txt
What's old is new again... except 100x more complex and likely more than necessary.