cMP3,1 - Play time.

[DCBassman]

This machine has been sat in its box, for sale, for a goodly number of weeks now. No takers who didn't ask stupid things of it and me.
So I got it back out, removed all the spinners, and put in the SSD I'd recently used on a MacBook Pro.
First off, I clean-installed El Capitan and then went for OCLP install of Monterey. Went well, took a very long time, but of course, fell foul of USB 1.1, which meant a wired keyboard would not work. Wired keyboard would only work at one keystroke per ten seconds after plugging in a PCIe USB3 card...
Got fed up with that fairly quickly, and tried Mint again. Same Bluetooth problems, so went for something completely different in Open BSD. That just boot-looped. Sigh.
So, vanilla Ubuntu. It doesn't have the Bluetooth problems that Mint has, and Mint in both Ubuntu and pure Debian flavours have this issue. Once it's installed, I'll write more, as I've not tried Ubuntu for many a year...

 

[joevt]

Use a USB 2.0 keyboard or connect USB 1.1 keyboard to a USB 2.0 hub, then connect USB 2.0 hub to MacPro3,1.
What PCIe USB3 card did you use so other people can avoid it.
Connecting mouse/keyboard to a USB3 card isn't a good idea because you can't use USB devices connected to that with the Apple Startup Manager to bypass OCLP or select a different startup item (unless you put the XHCI EFI driver into your ROM?).

 

[DCBassman]

Use a USB 2.0 keyboard or connect USB 1.1 keyboard to a USB 2.0 hub, then connect USB 2.0 hub to MacPro3,1.
What PCIe USB3 card did you use so other people can avoid it.
Connecting mouse/keyboard to a USB3 card isn't a good idea because you can't use USB devices connected to that with the Apple Startup Manager to bypass OCLP or select a different startup item (unless you put the XHCI EFI driver into your ROM?).

To be honest, I was just messing around. No idea that any keyboards themselves would make a difference! No idea of the USB3 card's ID either, although I can find out when I remove it later.
Anyhow, Ubuntu working well, including Bluetooth!