Minix was generally distributed with Andrew Tanenbaum’s book. When I installed it on my 286, it was on 3.5” floppies — two dozen or so.
I do remember that many floppies for Win95 and Slackware, though a few years later.
My PS/2 HDD was only 20MB, and I recall having enough free space after the install. For Minix 1.5, there's another estimate here of 9 DD floppies -- 6.5MB compressed. That seems about right.
I definitely went for the compiler and all the accessories. The C compiler was far from ANSI-compliant and barely K&R. It made for some interesting times.
Minix 3 is BSD-licensed, and distributed on CD-ROM now, and can still be purchased from Pearson! https://www.pearson.com/en-us/subject-catalog/p/operating-sy...