The Macchina Community Showcase is the go-to place to find the latest links to libraries. A specific project, such as M2RET, may have its own requirements so it is worth checking with your project. At this time, M2RET no longer needs its “own” versions of libraries and links to the onces from Macchina and other upstream sources (which are the same as listed on the Showcase.
I apologize for any confusion that has been caused. Other than a brief period of time when M2RET started pointing to Macchina’s SD Card library before that library the additional modification made for M2RET I thought links were always correct.
With the inclusion some libraries in the boards package and the Arduino IDE’s update notification feature this should hopefully be less of an issue. If there are libraries that are commonly used/updated but not included in the boards package, there would be the option of getting them listed in Arduino’s Library Manager to gain update notification and easy installation or adding them to Macchina’s boards package.