Is check an external plugin that doesn’t ship with beets? If so, you might consider asking the author who maintains it. (And that might also explain why you aren’t finding it installed on your system.)
Ooooooh, that makes sense. I see now it was included under the section for plugins written by the community. I saw no instructions on how to add the plugin so I assumed it was included.
If you could do a quick glance, could you make any guessing on it being significantly different than the bad files plugin? Talking about the recognition process itself rather than the configurations available.
Hmm… I’m not an expert on this, but it looks like a primary difference may be that beets-check can store checksums in the database. This can help you detect when another tool, or even your hardware, corrupts your files. The badfiles plugin doesn’t do that; it just runs off-the-shelf validation tools