Humor can give grief a brief window without asking grief to leave the house.

Laughing in the middle of loss is not a betrayal of it. Grief does not need constant solemnity to be real, and a joke at a funeral is often the room breathing rather than the room forgetting. The window humour opens is short and it closes again, and both of those facts are fine.

If laughter arrives while you are grieving, you can let it come without interrogating yourself afterwards. And if you are near someone in loss, follow their lead rather than deciding in advance what tone is respectful. Holding both at once is something people manage more often than they expect.