I’ve not heard of a modern version of Linux that will fit on a floppy, the kernel is too big these days. You would need to cut it down to the drivers for your exact system and nothing else, and even then it probably wouldn’t fit. The compressed kernel on my machine is 8MB, and that’s with a lot of drivers not compiled into it but living in modules. You could make it quite a lot smaller by building for i386 instead of x64, but the best you could hope for is maybe half the size. And then you have to get some actual applications software on to the floppy as well…
Tom’s rtbt is based on linux version 2.2… which is like 25 or more years old!
Of course menuet OS still fits on a floppy… but it’s written in assembler http://menuetos.net/