ktfmt 0.31 was just released which includes a couple breaking changes for Spotless. Specifically

• Library usage was updated to make the format method no longer be a top-level method. It is now inside the Formatter object.
• The binaries for 0.31 appear to have been published to Maven Central's new S01 infrastructure, which means the dependency needs to be resolved from https://repo1.maven.org/maven2 as opposed to https://repo.maven.org/maven2.

I'm not super familiar with reflection so it might take me a day or two before I can propose a PR for at least the first part of this. Let me know if you'd prefer to do it yourself faster.