> QNX had a "free as in beer" distro that fit on a floppy, with Xwindows and modem drivers.

I don’t think that had the X Windows system. https://web.archive.org/web/19991128112050/http://www.qnx.co... and https://marc.info/?l=freebsd-chat&m=103030933111004 confirm that. It ran the Photon microGUI Windowing System (https://www.qnx.com/developers/docs/6.5.0SP1.update/com.qnx....)

Somebody has build it: https://membarrier.wordpress.com/2017/04/12/qnx-7-desktop/