Sadly, it does not seem to boot on my 486 DX2, I even stuffed 32M of RAM into the machine (8*4M, maximum the mainboard supports), more than the recommended 20M.
I have copied the floppy image from the site. It churns for about a minute and a half, loading kernel and initrd, then says "Booting kernel failed: Invalid Argument" and drops into SYSLINUX prompt.
EDIT: I tried a few more floppies to rule that out as the cause of the problem.
Here are some screenshots: https://imgur.com/a/floppinux-0-3-1-Mdh1c0w
EDIT 2: I cloned SYSLINUX, checked out the specific commit and did some prodding around.
The function `bios_boot_linux` in `com32/lib/syslinux/load_linux.c` initializes errno to EINVAL. Besides sanity checking the header of the kernel image, there are a few other error paths that also `goto bail;` without changing errno.
Those other error paths all seem to be related to handling the memory map. I know that the BIOS in my machine does not support the E820h routine. I have a hunch that this might be the reason why it fails.
The website has an image gallery where people ran it on actual hardware: https://krzysztofjankowski.com/floppinux/floppinux-in-the-wi...
Most of those machines seem to be newer systems which probably support E820h, except for another 486 DX2 with a similar vintage as mine, that also failed to boot.
For my 486 distro[see snacklinux.org], I use syslinux 4.07 due to similar issues. I never had any luck with syslinux 6.x, I’d recommend a similar path. It always seems funny to me when I see similar projects, claiming it runs on 486 hardware but rarely do I see people actually doing that, and just fire up qemu instead. Running Linux in a vacuum isn’t realistic, especially when we’re talking old hardware and configuring IRQs manually.
It is running some AMI BIOS variant with a copyright date of 1992, I currently don't have the exact version string around to compare with the ROM dumps on retroweb. vbindiff says the "F" and "M" images are identical and the "H" only has a few 1-byte differences, mostly typos in ASCII strings.
I've written a small boot sector program once that tries out memory and CPU information gathering techniques, so I know the INT 15h, E820h, E801h are not implemented but INT 12h and INT 15h AH=88h return something sane. When I have more than 16M installed, the later reports the full 31M of HIMEM, but I'm not sure how the ISA memory hole factors into this.
From what I saw glancing at the scanning code yesterday, syslinux 6.x should fall back onto AH=88h if AX=E820/E801 doesn't work. It's interesting to know that this worked in older SYSLINUX, I'm curious to check out what changed.