I wouldn't be surprised if you could bit bang ISA these days. ISA ran at 8MB/s, and (e.g.) a Raspberry Pi runs at 1.5GHz. That's nearly 200 cycles per ISA clock. All you need is a couple of i/o pins.
https://raspberrypi.stackexchange.com/questions/100011/how-f...
However even a home silk-screened PCB could probably handle that and a USB control connection. Without deep knowledge hard part's likely the software, getting the connected item to work; probably as a virtual hardware device in a KVM or other emulated guest OS with the illusion it's on old hardware.
But it might work if ISA card doesn't rely on clock being constant all that much, then any jitter in CPU transfer shouldn't matter too much.
Might be possible, someone bitbanged (sending) ethernet frames.
This example makes me convinved that if you added a clock and some latches to a raspberry pi, it definitely should be able to do ISA bus.
Maybe even without any hardware, who knows. But it needs to level shift from 3V to 5V anyway.