Newby confusion on beets plugins

[John Huff]

I am so CONFUSED!

I am trying to get the replaygain plugin to work in beets.

I installed beets on my Debian 12 system via pipx and it seems to work.

I struggled to get the lastgenre plugin working but I fail to understand what I did to finally get it to work. Now I am wrestling with the replaygain plugin. I have installed ffmpeg as the backend but replaygain fails to configure. 

What am I doing wrong? 

The whole 'Read the Docs' section on installing/enabling plugins has failed to instruct me as to how to enable/install the plugins. How am I supposed to understand which plugins are natively available to Beets and which ones need to be installed, let alone HOW to install them. 

my config as included below

directory: /****/media/mlib
library: /t****data/beets/musiclibrary.db

plugins:
    lastgenre:
        canonical: yes
    replaygain:
        backend: ffmpeg