How do I install Minecraft mods on macOS There are so many mods for Minecraft and reading online everybody talks about a mods folder that I can't find. What's wrong with macOS and how do I get it working? 

I found the answer to this question and I'm posting these info as Q/A on this website in the hope that it can help someone.
After searching on Internet I discovered that MODS are not supported by the Minecraft authors, so you have to download external libraries and HACK your Minecraft installation.

You must download the Java edition, mods are available for this version, so the lack of macOS port is not a problem. You can download it from the Minecraft website

Once you downloaded it, click on the icon, this will open the Minecraft launcher, which is a frontend program to your game.



After the launcher ends loading, you will see a select button that allows you to choose the version you want to play.



Well, we need to create a patched version of Minecraft and after this, we can choose which one like to start using this selector. So now the question is: how do we create a patched version of Minecraft? We need to install the Minecraft forge that is an API that allows MODS to work with few or no issues. 

CLOSE YOUR MINECRAFT.

You can download it from: Minecraft forge

Which version to download depends on your Minecraft version! You can see that my Minecraft version is 1.14.4, so I need to download this version. The file you have to download is the INSTALLER:



After the installer download completes, start it and wait it ends its work. Now you can start again the Minecraft launcher and you notice that there is something new: the patched version is ready!!



Start again Minecraft, it will take longer to get ready and will download any missing library. Once it starts there is another important surprise for you: you got the mods folder!

Where is it?! Open a terminal and copy and paste this: 

open ~/Library/Application\ Support/minecraft  


a new finder window opens and there you can see the mods folder



There you have to insert all the mods you want. Remember: with Minecraft version x.x.x works only the mod build for this version! When you search for mods, be sure to download the correct ones.

Have fun!