Darkvision can prevent the function of Nature’s Mantle.
Nature’s Mantle says:
While you are in an area that is lightly obscured, you can Hide as a bonus action even if you are being directly observed.
So typically, when in dim light, you are lightly obscured. But, Darkvision says:
A monster with darkvision can see in the dark within a specific radius. The monster can see in dim light within the radius as if it were bright light.
With respect to a creature with Darkvision, you are not lightly obscured while in dim light, as they can see in dim light as if it were bright light.
It becomes complicated when there are multiple observers with and without darkvision.
It gets weird when the Nature’s Mantle wearer is being observed by a creature with, and a creature without darkvision.
With respect to the creature without, they are lightly obscured, but not with respect to the creature with. In this scenario, I would allow the bonus action hide, but it would not hide the wearer from the creature with darkvision, only the creature without it.