It appears that many ovens will run @ 150 deg. F (warm, defrost, etc.) and 20 minutes of that should zap any virus.
HOWEVER, if the oven elements run hot (esp. glowing hot), direct radiation might get the mask hot enough to damage it even though the air temperature in the oven is only 150 deg. (This is like asphalt under one’s feet on an 85 deg. sunny day.) A mask has low mass / thermal inertia, so it would heat up quickly. A convection setting (if available) should help.
This said, I used a temperature gun on a N95 mask in our big toaster oven set on “Defrost” and the mask did not seem to be getting over 155 deg. Granted that the mask being low thermal mass would start cooling the second cooler air comes in the oven door.
OTOH, looking at the Lancet table, it appears to me one could warm the oven to 150-160 deg F, turn it off, quickly pop in the mask (masks in a larger oven) & close up, and let it all coast for 30 minutes. If paranoid, pull the mask out and repeat.
Disclaimer: I’m not an expert and have no way to test the above for virus “baking” reduction or mask performance later, besides looking for obvious mask damage.
“Scientists were close to a coronavirus vaccine years ago. Then the money dried up.”