In 1991, William & Lynne Jolitz released their "Excellent Operating System" - 386BSD. It occupied some 30 floppies but they got hundreds of thousands of downloads. Unfortunately their OS demanded an FPU, which was a separate and expensive chip, so Linus and others took a different route, and 386BSD didn't take over the world. It's described here as the first open source OS, but it seems external contributions were not welcome.
"Hunger for 386BSD fed by the Dr. Dobbs Journal article series led to an estimated 250,000 downloads from the Internet in the first week"
The series of articles about porting BSD to the 386 can be read athttp://porting-unix-to-the-386.jolix.com/three-initial-pc-utilities
"Just in case anyone is wondering, the entire 386BSD system was created on a 386SX laptop with three Mbytes of RAM and one 100-Mbyte disk."
Rather later, in 1994, and probably too late, Dr Dobb's published a CDROM with a 1.0 release. The liner notes can be read here:https://jolitz.telemuse.net/c/the-386bsd-release-10-cdrom-liner-notes/246837681
If you feel brave, you can run 386BSD in emulation on Bochs:http://gunkies.org/wiki/Installing_386BSD_on_BOCHS