It is indeed possible to write Vaadin 10 Flow apps in Kotlin. Here are a couple of resources to get you started:

• Two introductionary videos, 40 minutes total running time, which explains the ideas behind Vaadin 10 Flow and behind the Vaadin-on-Kotlin framework itself:
  • Vaadin-on-Kotlin Flow Part 1,
  • Vaadin-on-Kotlin Flow Part 2

Those videos will also help you to download and start with the very simple skeleton application.

• The skeleton application which contains everything necessary to build the app and launch it, and it only introduces a very simple UI: a button and a text field. You can find all the necessary information here: karibu10-helloworld-application
• A more polished application which shows additional components and also demonstrates the ability to connect to a Polymer Template: the Beverage Buddy application. It has no database access support and only serves in-memory dummy data. It is a part of the Karibu DSL framework; instructions to get it and launch it: Beverage Buddy.
• The same Beverage Buddy application as above, but uses an embedded full-blown H2 SQL database and is based on the Vaadin-on-Kotlin framework: Beverage Buddy.

Please feel free to post any questions at the Vaadin Forums.