data point.
I have most recently tried and used this gradle plugin:
id 'org.hidetake.swagger.generator' version '2.16.0'
Took a few tries at others to find the one with the versions of codegen that worked for me. its not anything fancier then a plugin for swagger-codegen, but does work and supports ALL the parameters (ya the ones you cant find in the docs) for codgen.
Recently used it to codegen a java and kotlin set of client API's for a public swagger API.
Easily accepted some template mods and confiigs to 'tune' the kotlin codegen, particulary the class names if the spec doesnt use operation id.