Yes there is a project for this one sec

Here check this link

http://www.alexandrugroza.ro/microelectronics … face/index.html

And

www.alexandrugroza.ro/microelectronics/index.html

I have an old ISA Diag card called the "Discovery Card" from 1993 that does similar but OP says no more open ISA slots so.....here is my quick take:
You have data lines, address lines, IRQ lines, DMA lines and some control lines. You really cannot just tap one and feed direct to an LED without messing with stuff.
I suppose you could take off ISA pin B13 : /IOW = I/O Write and feed it to a transistor using it as an inverter/buffer then to a R/C network then to a LED so it "flickers" when active, otherwise it would be either on or off like a floppy drive/HD led AFAIk.
That way any time ISA bus data writes are done you would see it. just a guess...and am probably totally wrong 😁