I seem to recall good support for PC98[0][1] was seminal. Our friend ‘washbear has notes[2], which might be touching on (eg) KAME[3] too.
[0] https://en.wikipedia.org/wiki/PC-98
[1] https://hackaday.com/2023/12/26/the-strange-world-of-japans-...
[0] https://en.wikipedia.org/wiki/PC-98
[1] https://hackaday.com/2023/12/26/the-strange-world-of-japans-...
If you were a Japanese enthusiast who wanted to have a "real UNIX" on readily available hardware, NetBSD and FreeBSD were relatively more accessible