I have an sbt file inside ~/.sbt/2/plugins/ and ~/.sbt/1.0/plugins. These files only contain a build info plugin declaration:

addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.13.1")

When I start an sbt 1.x project and type plugins, I can see that the BuildInfo plugin is loaded. I can use settings like buildInfoKeys.
However, when I start an sbt 2.x project and type plugins, the build info plugin isn't available, and I see errors when trying to use something like buildInfoKeys.

What's interesting is that if I make a typo in the sbt file inside ~/.sbt/2/plugins/, an exception is thrown, so sbt reads/detects the file - but it seems like it's not actually loaded.