Yeah, "dual mode" or "PS/2 Compatible" used to be listed on many boards, but not anymore. I cant recall the last time I've see it listed outside of eBay.
Thankfully, like
@BruceMcF said, a majority of keyboards still support it, even if they don't advertise it anymore.
The two 60% boards I have,
https://amzn.to/3VR38PL &
https://amzn.to/3CPwHIM don't support it, and I assume it's because of all the "special functions" used to access all the combined keys. I like these boards for their small size and portability and use them on my Raspberry Pi units as needed.
Thankfully, the cheap
Rii Primer 10-keyless boards I like work perfectly. I use one on my bench computer and the other is on my home server.
That all being said, I'm seriously thinking about buying a
Perixx Periboard for the Z80-MBCs build. Plus, I just love the old-school IBM Model M look and reasonable asking price! I already know it's adapter compatible since a friend uses one on an old DOS/Windows 95 system he uses for retro gaming.
EDIT: It's a good thing I double-checked my base 3D design. I had 2 supports for the uTerm in the way of the MBC2, and I forgot about the SD card and RTC module mounting.
? I tripped-checked it, and it "should" be ready to print now!
A classic geek & family man who enjoys all things retro! Computers, hardware, games, electronics, etc. Expert at nothing, professional hobbyist, and old-school blogger!