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So you say there is an absolute, undisputable, single answer. There is no graded scale.
Then there are only two alternatives: No joking whatsoever is acceptable. Or anything is acceptable. I suspect that you go for the first alternative.
I am not sure if the Norwegian term "galgenhumor" can be directly translated to English: "Gallows humour". It refers to the kind of jokes a delinquent makes before he is killed. Or in a more modern setting: Making jokes on in an extremely bleak situation, about that situation, to make people laugh at at to keep spirits up. A special kind of black humour, the one that is not just black, but refers to your own current situation. I dare to claim that this sort or humour has saved a few lives: When people can laugh at their own situation, they may gain the strength to survive it.
I accept that you think it is better to keep the situation as bleak as possible, smile at nothing, laugh at noting that is related to it. So you are free to ignore all such things. Consider my request to be directed at those who think humour can be an essential element in handling hardships. It is not evident how far the joking might go, and it certainly varies from one society to another, one setting to another. It is not at all obvious that a joke crossing the border line in one specific society in one specific setting could not cause a releaving laugh and give a mental push to people ina completely different setting in a completely different society.
Then there are only two alternatives: No joking whatsoever is acceptable. Or anything is acceptable.
Joking about people who have died is unacceptable, because their families are in mourning.
Joking about the reason the virus spreads through certain communities is unacceptable, because it will almost certainly be racist.
OTOH, jokes like Pompey3's saying he now farts to hide a cough is perfectly acceptable.
You should think two things, before telling a joke about the coronavirus:
0: Will I be adding to anyone's pain, by saying this?
1: Will saying this make me look like a completely heartless and/or self-centred dick?
In fact, don't restrict those rules just to jokes about the coronavirus. Apply them every time you're thinking of opening your mouth to speak -- unless, of course, you really are a heartless/self-centred/racist dick, in which case it's best if everyone knows about it.
I wanna be a eunuchs developer! Pass me a bread knife!
A horse walks into a bar. The bartender asks the horse if it's an alcoholic considering all the bars he frequents, to which the horse replies "I think not!" POOF! The horse disappears.
This is the point in time when all the philosophy students in the audience begin to giggle, as they are familiar with the philosophical proposition of Cogito ergo sum, or I think, therefore, I am.
But to explain the concept aforehand would be putting Descartes before the horse.