Might not be a defective processor but rather possibly a bad batch of defective processors when made at the factory.
If the processor was truly defective than all those symptoms would occur on every hardware that processor was installed in, correct?
Just guessing but I imagine over half a million laptops or PCs have those processors installed. If it was defective than those manufacturers of laptops and PCs would be spending huge amount of money on Warranty tickets to replace the processors.
If that was the case than AMD would be well aware of any possible defects in the processor because the manufacturers would be breathing down AMD neck to fix the issue.
Plus the Manufacturers of Laptops and PCs have their own engineering departments that can verify if the issue is a defective processor thus notify AMD.
So far I haven't heard of any recalls on those AMD mobile processors from AMD nor any articles from Tech sites mentioning those processors as being defective.
You live in the EU so you have automatically a 2 year Warranty from the EU Retailer under EU Consumer laws.
You should have used your laptop more often during the 2 year Warranty range to make sure your laptop was working correctly. But in your case, you were negligent in that respect.
Now the 2 year EU Warranty has expired and now you decide to use the laptop extensively and find out you have all types of major issues with it.
I would believe many EU Retailers would be complaining to the European Commission and AMD if they have a large percentage of laptops and PCs returns under Warranty due to a defective mobile processor.
EDIT: Since you are not using Windows drivers for your AMD IGPU that could be the reasons for your green screens and crashes or instability. Most likely it isn't the processor but the Linux drivers that are causing your problems.
All your issues are due to the IGPU and not the actual processor. The IGPU run on AMD Graphics driver so if you have a unstable or incompatible graphics driver you will have graphic or video issues such as the ones you are having.