Continuing the discussion from Thermal paste:
Shortly after Lockdown began my iMac went Tonto and packed in. Watching a video on YouTube I was informed that it could be the Graphics card giving up the ghost. Only course of action was to take the computer apart and remove the Graphics Card and bake it in the oven for 10 minutes at 190C which I duly did. I ordered the thermal paste which arrived from Greece and took four days to arrive. Liberally applied to the relevant Processor and support chips and Transistors and hey pesto one functioning iMac.
I kid you not. Defies all logic but it works!