Have you tested this on an actual 486?

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.