Two layers
On the top layer the layer mask should be just black (for transparency) and white (for opaque)
You can get that using fuzzy select with a low (4 or 5) threshold value on the background. (or any other way you prefer)
The resulting selection creates the mask Layer -> Mask from selection (inverted)
Then adjust the top layer as required.
example: https://i.imgur.com/UOjWPhj.mp4
On the top layer the layer mask should be just black (for transparency) and white (for opaque)
You can get that using fuzzy select with a low (4 or 5) threshold value on the background. (or any other way you prefer)
The resulting selection creates the mask Layer -> Mask from selection (inverted)
Then adjust the top layer as required.
example: https://i.imgur.com/UOjWPhj.mp4