How do I merge 2D maps?

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Hello,
I am using the gmapping package to create a 2D map.
One of the targets for my robot is an environment where the layout changes with a certain frequency.

It would be difficult to change the entire map every time the layout changes, so I am thinking of a mechanism to partially update the map.
After some research, I found an example of using a scan matching algorithm such as ICP algorithm to combine 3D maps.
Is there a package to implement such a mechanism for 2D maps?
Or do I have to join the maps by hand?

If anyone is doing something similar, please let me know.

Thanks in advance.