buildSrc and normal module plugin in one project

I have project which has defined plugin in buildScr folder exactly like this

Then I have normal module called plugin which is my main gradle plugin module which I want to deploy as library to maven repository.

But this project is part of buildScr compilation thanks to

project(":plugin").projectDir = File(rootDir, "../plugin")

inside of buildSrc/settings/gradle.kts

When I define inside of plugin module

 plugins {

in plugin module it fails with

* What went wrong:
Error resolving plugin [id: ‘org.gradle.kotlin.kotlin-dsl’, version: ‘1.3.6’]
> Plugin request for plugin already on the classpath must not include a version

So I tried to skip version by adding

plugins {

A it fail on exactly the same line with

* What went wrong:
Plugin [id: ‘org.gradle.kotlin.kotlin-dsl’] was not found in any of the following sources:

- Gradle Core Plugins (plugin is not in ‘org.gradle’ namespace)
- Plugin Repositories (plugin dependency must include a version number for this source)

Why did it happen?
I’m using Gradle 6.5.1