v2 is for QGIS 2.x
v3 is for QGIS 3.x (developed with QT 5.13 and QGIS 3.8)
2020-12-07:
For QGIS 3.16 on MacOS Catalina and Big Sur you might have to upgrade Pillow:
$ cd /Applications/QGIS.app/Contents/MacOS/bin
$ ./pip3 install pillow -U Collecting pillow Downloading Pillow-8.0.1-cp37-cp37m-macosx_10_10_x86_64.whl (2.2 MB) |████████████████████████████████| 2.2 MB 2.7 MB/s Installing collected packages: pillow Attempting uninstall: pillow Found existing installation: Pillow 7.2.0 Uninstalling Pillow-7.2.0: Successfully uninstalled Pillow-7.2.0 Successfully installed pillow-8.0.1