Turns out the first time I sent my Gigabyte RX5600XT card to the seller as part of the warranty process, they didn't even send it to Gigabyte and sent the card back to me unfixed and still crashing. Also explains why GB says they never had the card in their system.
Had to tell the seller I really want the card sent to GB this second time.
My tech tip: If your PC crashes & restarts itself, when you open the Event Viewer afterwards, don't bother with Event 41 Kernel-Power and Event 6008 EventLog, these only mean that your PC didn't shut down correctly.
Instead look for other errors that happen around the time of the two events, for example BugCheck or WHEA-Logger for example, those are the real errors.
Absolutely love it when I search for specific computer problems on Google and 90% of it are helplessly generic advice from fake tech sites. And another 5% are forum threads with zero replies or only 1 automod reply.
RX 5600 XT is away for warranty process and they say it'll take 1 month, RX 580 is outright dead, only the RX 550 and R3 3200G's iGPU remain. A weak graphics card is better than a dead one or a non-existent one, looks like I have to live with the RX 550 for a while.
And dang does my mouse cursor stutter a lot with the RX 550. Anyone who reads this, can I know how to not make the cursor stutter?