Can not give much advice other than just tried in a (k)ubuntu 18.04 VM and it compiles there. The code is basically 10 years old, so there are any amount of deprecated procedure warnings, but that is all they are, warnings, it compiles.
or
Are you using a Gimp flatpak or snap. These are 'sandboxed' you can not use for compiling.
Attached the compiled plugin and the output I got, it might give a clue. Unzip, pop the wavelet-denoise file in ~/.config/GIMP/2.10/plug-ins/ Check the permissions, should already be executable but check anyway
Another source that has a similar function is the gmic_gimp plugin where there is a smooth(wavelet) in the Repair section.
Quote:It falls short when attempting the 'make' with errors of not identifying the location of the GIMP main program and such...Do you have libgimp2.0-dev installed? that pulls in lots of dependencies for compiling plugins.
or
Are you using a Gimp flatpak or snap. These are 'sandboxed' you can not use for compiling.
Attached the compiled plugin and the output I got, it might give a clue. Unzip, pop the wavelet-denoise file in ~/.config/GIMP/2.10/plug-ins/ Check the permissions, should already be executable but check anyway
Another source that has a similar function is the gmic_gimp plugin where there is a smooth(wavelet) in the Repair section.