Working example with Polymer 3 and lit-html
Extending the PropertyAccessors class from the Polymer mixins I was able to use lit-html for rendering.
I created a PolyLitElement trying to replicate the Justin Fagnani example slide from the Polymer Summit 2017 that use the _propertyChanges from the accessors for rendering the content, calling the render() method of lit-html from the super-class.
Just check the source code to understand better and fill an issue if I'm making mistakes! This is actually a first try following the advice of Justin.
yarn build # Just build the bundle
yarn start # Run http-server on src folder
yarn dev # webpack -w
yarn test # xo