Here I tried to do as little as possible to get http4s running using ZIO instead of cats-effect IO
Follow the standard http4s instructions and get the quickstart app running:
sbt -sbt-version 1.2.8 new http4s/http4s.g8 -b 0.20
You can see the result in this commit:
Instantiate the Quickstart Server with a ZIO Task instead of the default cats-effect IO: