Version for Gimp-2.10.30 Win 64 bit attached.
In menu: Tools➤GEGL Operation➤Cutout Effect

Place the file in gegl plugins in a directory: C:\Users\<your-user-name>\AppData\Local\gegl-0.4\plug-ins
Find the plugin in: In GIMP menu; Tools> GEGL Operation

Just like any third party plugin that you place in your;
C:\Users\<your-username>\AppData\roaming\gimp\2.10\plug-ins
The best place to place this plugin and other Gegl plugins is in you your Local Windows folder. This is your best choice in case you upgrade your GIMP version and the Program directory C:\Program Files\GIMP 2\lib\gegl-0.4 gets overwritten.

Congratulations.
I can now calmly go into a state of rest.

Just for clarification (reminder) on Windows:

1. Using unins000.exe (recommended) will not remove files added to c:\Program Files\Gimp2\ after installation, so before installing a newer version in the same location (the installer will ask if you want to use an existing directory - and if YES - will remove all files from it), you can make a backup (of the add-ons) if you still need them.

2. If you accidentally install duplicates (very bad practice ) in both folders:

a. [global - for all versions of Gimp from gegl-0.4 of a given user, also for portable versions at any location]:

C:\Users\ <username> \AppData\Local\gegl-0.4\plugins\

and

b. [locally - only for a specific Gimp version]:

C:\Program Files\GIMP 2\lib\gegl-0.4\ or [portable] e.g. d:\Gimp-2.10.30_Portable_32-64bit-Win\lib\gegl-0.4\

will be used with path b.

3. Regardless of which installation path you have chosen (a or b), you can put them in subdirectories according to the Rich2005 hint .

4. The latest versions of msys2 (I checked those: msys2-x86_64-20220503.exe and msys2-x86_64-20220603.exe) do not create files compatible with Gimp-2.10.30 (from gimp.org), so if it stays like that (and nothing indicates that this will change) the next version of Gimp will "break" all old plugins (* .exe and gegl * .dll), so you will have to recompile anyway (which with some old * .exe plugins can be virtually impossible, then you'll only be able to use them while keeping the old version of GIMP).

I would very much like to be wrong about the theory from point 4.

Yes, I think that you deserve a rest (you read my mind)

Thank you Marek, for that explanation and letting us know about other choices. Some users still have the habit to uninstall through the Control Panel like me. That is why I preferred to place every 3rd party stuffs in the local directory.