This is a known issue and not related to your graphic card issue. Apple removed the support for USB 1.1 device. This is why your cMP cannot recgnoise the USB mouse (a USB 1.1 HID) if you connect it "inside" Monterey. But if you plug that into the USB port before boot, it will just keep working. Or the work around is to connect the USB 1.1 device via a USB hub.
Anyway, back to your graphic card issue. According to your decsription. It sounds like a hardware failure.
Full fan speed from the graphic card for no reason isn't a good sign at all. Especially if you just power it on, but not stressing the card inside macOS.
If you suspect the Pixlas mod causing the issue, you can buy some cables to power the Radeon VII in this way
Can. However, my recommendation is balancing the demand between the mini 6pins. If you re-read my post #35 again, you should able the see that the power draw via each mini 6pin is very balanced. The reason is because I use a cable combination to balance the demand. "DUAL mini 6pin -> Single...
forums.macrumors.com
I created a kext for the Radoen VII to run safely with mini 6pins only (at least good for short period of time)
I confirmed it's possible to run a radeon VII with the mini 6pin ONLY (no Pixlas mod, no extra PSU, no SATA power, but with power balancing) with my PowerPlay Table kext. I limit the card's power draw to 204W (170 x 120%). This is NOT a random number, but when I perform tests in Windows, I...
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You may try this with just using the mini 6pins to power the card. I can't guarantee your card's silicon quality is better than my card. So, I can't guarantee your card's stability under stress (with that kext). However, it should be good enough for your to boot to desktop, browse the web, watch videos, etc.
If you are happy to inject codes into OpenCore, you may even further lower the Radeon VII's power draw by injecting this code (in this case, no need to apply the kext above).
But if your card shows the same behaviour with the mini 6pins. Then either the PSU itself is bad (not enough power to the card no matter how you connect them together). Or the PCIe slot is bad (this is easy, move the card to slot 2 can confirm / fix it). Or the card itself is bad.
If it's a graphic card failure, there is not much you can do about it. Radeon VII should be out of warranty already. All you can do is basically open it up, have a look if anything loose / broken. Re-apply thermal paste [P.S. the original graphite pad is really good. Open the card most likely will break that pad. AFAIK, there is no thermal paste can do better than that graphite pad. The only better solution is liquid metal. But if you have concern about liquid metal, please make sure you use the absolute best thermal paste you can get (at reasonable price, of course)].
Since the graphite pad won't dry up, it should just work. So, I don't think re-paste itself can help anything. However, open it up, clear the dust, may bring some circuit back to normal. This is entirely possible.
If this doesn't help, then the last thing you can do is the bake the card (many videos on Youtbube about this). It may bring the card back, but usually will fail again after few months. This is pretty much just for you to buy time to get another card.
