The PC-type floppy controller is bound to ISA kind of. It uses ISA DMA, port addresses in ISA memory space etc.
That's why motherboards had SuperIO chips on-board and after them, LPC bus.
They're essentially both working like ISA from a software view.
Anyway, special PCI floppy controllers did exist.
That catweasel card for PC allowed interfacing Amiga floppy drives, SID chips and Atari style joysticks.
The old version used ISA, the new one used PCI.
However, they didn't show up as legacy floppy drives under DOS, I believe.
https://www.vesalia.de/e_catweaselmk4.htm
Edit: The LS-120/LS-240 drives used IDE and could read 1,44MB diskettes.
With special BIOS support, the drives worked fine in DOS, just faster.
Edit: Speaking of strange ideas.. I have them, too. 😁
I play with the idea of building a Pentium II/III PC for plain DOS.
To run very complex/demanding software for DOS.
Raytracing, MOD Trackers with 30 channels, AdLib Tracker etc.
However, I'm playing with the idea of going to install an ISA VGA card on a higher clocked ISA bus.
Why? Because all of the PCI VGA cards have do so many limitations.
No mode utility for CGA/HGC/EGA, no advanced text modes, no old Super VGA compatibility (DOS programs do not know new models), VBE 3 broke compatibility etc.
Also, they're not so much register compatible anymore. Demoscene productions expect ET4000 era compatibility, for example.
Yeah, I know. It's a silly idea. But at medium resolutions, that may work.
"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel
//My video channel//