The first one that came to mind was fli4l (Floppy ISDN for Linux). Originally a distro of German origin that fit on a single floppy disk to turn a 386 or 486 PC into a router for ISDN connections. Last I looked it’s still actively worked on.
There are probably tons of more obsuce ones. But this is one I actually used.
Doesn’t Pop!OS do that already?