I see that the latest eslint-plugin/package.json seems to require ESLint version 5.x.x:

{
  "name": "@typescript-eslint/eslint-plugin",
  "version": "1.12.0",
  . . .
  "peerDependencies": {
    "@typescript-eslint/parser": "^1.9.0",
    "eslint": "^5.0.0"   // <------------ ???
  }
}

The ESLint 6 was released a month ago. Is @typescript-eslint/eslint-plugin only compatible with ESLint 5?

If it's known to be compatible, maybe we should update the peer dependency. The toolchain I'm using validates that peer dependencies are correctly installed, so this is preventing us from upgrading to ESLint 6.