The read-more Pelican Plugin was the second one I helped to migrate to the new Structure / GitHub Organization.
After a specified length, it adds a "read more" link the the Posts Overview, you can see it on this Blog in action for example.
The Configuration is very easy, the Plugin supports a few Parameter for your pelican.conf File.
It can by installed by running python -m pip install pelican-read-more, the Source is available on https://github.com/pelican-plugins/read-more