There is a Scala 3 version available for scalacss "core". See [here](https://mvnrepository.com/artifact/com.github.japgolly.scalacss/core_3/1.0.0). but for "ext-scalatags", there is only: [this scala 2.13 version](https://mvnrepository.com/artifact/com.github.japgolly.scalacss/ext-scalatags_2.13/1.0.0). Since they are in the same source tree, I would have assumed they would both have Scala 3 versions.