I imagine the post you are replying to is referring to actually getting the Linux kernel to boot (since there is no BIOS, UEFI, etc.) and writing drivers for all the possibly specialized hardware Apple put in there.
The main issue might be video drivers and other non-standard hardware. There are many reports of people being able to boot into linux on the new M1 by tweaking secure boot.
The way I understand these reports is "it's most likely possible, but we still need to actually make it work". In particular, it seems there's not a complete boot loader.
