Going to the other extreme.

So someone quite young died of Covid, someone else question if this person may have had serious health problems that may have already been life limiting and asking if this person died of covid or with it. Chances are if they didn't die of covid they could have died of the flu or one of many other diseases if that was the case, Freddie Mercury dying of Pneumonia when he had AIDS comes to mind.
Anyway, someone else went to the complete other extreme and said "I'm pretty sure he wasn't ran over by a bus". I'm pretty sure if someone who was ran over by a bus who just happened to have covid being declared to have died of covid is the complete other extreme.
When people do that, to make a point in argument is there a name for that.

So...one person suggested they could have died from disease, and another says they couldn't have been hit by a bus...?

Where's the fallacy?

It's just people speculating on how a young person passed away.

If it's implied they either died from disease or were killed by a motor vehicle, this would be a dilemma (either true or false).

Extremes usually suggest the "Fallacy of the Excluded Middle."

There are no arguments here, but question, to which no complete answer has been given.
I will make an analogy to check if I understood the context well:
Q: Is this car black?
A: I'm pretty sure it isn't as white as snow.

The car, of course, can be other colors, red, blue, gray...