The only PCI-card installed is an ATA-card that the HDD is connected to, since the built in bus only supports a maximum drive size of 128GB on the 2001 QS.
It may be a pain to pull that card out, but I think it's worth a try. The error you got seemed to suggest it's an issue with a PCI device connected to it. Of course, I could be wrong, but without any other leads, it's all we know.
What is really so special about Jaguar ? Unless someone can tell me a modern browser can run on it, its not worth it to run it, really we all should be using Linux as Leopard is not safe anymore.
It's the latest OS that runs a lot of Mac OS software that Panther, Tiger and especially Leopard and non-Apple systems cannot. Others may like the look & feel, too. Other than that, hardly much reason. But all this is already more than enough reason.
True safety is only possible if your computer is an air gap computer (zero networking and zero usage of devices that were once connected to the device in other devices). Having PowerPC Macs (as opposed to Intel/AMD/ARM computers, from Apple or otherwise) is already a security bonus (no CPU-level backdoor). GNU/Linux extra security only if you use a libre distro, the closest to which is Debian (on PowerPC), assuming you install only libre software, drivers included, avoiding any binary blob. All other systems have binary blobs. But even if you do all this, security flaws are everywhere, and there's certainly intelligence interest to keep things that way as much as possible.
Mac OS X by most standards is pretty "secure", though, as far as practical matters are concerned, and as far as recent OSes are concerned. But you are more than free to make any choice you'd like.
(There's an image of that in the MG, btw. Thing is from 1983.)
