This shows an error publishing to maven central when using single variant publishing from AGP in combination with com.vanniktech.maven.publish.

To reproduce execute

./gradlew publishToMavenCentral

The error is

FAILURE: Build failed with an exception.

* What went wrong:
A problem occurred configuring project ':mylibrary'.
> Using singleVariant publishing DSL multiple times to publish variant "release" to component "release" is not allowed.