I write Kotlin JVM libraries and some browser automation, mostly derived from needs on my commercial projects.

Validk - A validation framework for Kotlin. Includes context-aware and conditional validation.
Alkemy - A browser automation framework written in Kotlin and based on Selenium and Kotest
RDF4k - A Kotlin library for working with RDF
kbods - A set of Kotlin libraries for reading and importing beneficial ownership data in the BODS JSON format