Use scoped CSS in Vue components from library (no data tags) - vuejs3

Question

When building a reusable Vue component library, the scoped CSS is not applied, because the PostCSS data-tags are missing. (If the component is not imported as a package, but directly imported into the project it works as intended: styles are applied, and data-tags are present, so the SFC itself is okay.)
https://vuejs.org/api/sfc-css-features.html
I'm building the components use Vite, so maybe it's something to configure in vite.config.ts?
vite.config.ts
import { fileURLToPath, URL } from 'node:url'
import { defineConfig, type PluginOption } from 'vite'
import vue from '#vitejs/plugin-vue'
import vuetify from 'vite-plugin-vuetify'
import typeScript2 from "rollup-plugin-typescript2"
import { visualizer } from "rollup-plugin-visualizer"
export default defineConfig({
plugins: [
vue(),
vuetify(),
typeScript2({
check: false,
include: ["src/components/*.vue"],
tsconfigOverride: {
compilerOptions: {
sourceMap: true,
declaration: true,
declarationMap: true,
}
},
exclude: [
"vite.config.ts"
]
}),
visualizer() as PluginOption
],
resolve: {
alias: {
'#': fileURLToPath(new URL('./src', import.meta.url))
}
},
build: {
cssCodeSplit: false,
lib: {
entry: './src/components/index.ts',
formats: ["es", "cjs"],
name: "CommonVtfyPlugin",
fileName: format => (format == "es" ? "index.js" : "index.cjs"),
},
rollupOptions: {
external: ["vue", "vuetify", "vuetify/lib", 'vuetify/lib/util/colors.mjs'],
output: {
exports: 'named',
globals: {
vue: "Vue",
vuetify: "Vuetify",
'vuetify/components': "VuetifyComponents",
'vuetify/directives': "VuetifyDirectives",
'vuetify/lib/util/colors.mjs': 'colors'
}
}
}
}
})
The Single File Component:
<template>
<v-select
:class="{'nkd':isNkd}"
....
>
....
</v-select>
</template>
<style scoped>
.nkd :deep(.v-field__input) {
padding: 0;
min-height: auto;
}
.nkd :deep(.v-field) {
padding: 0;
align-items: center;
background-color: transparent;
}
.nkd :deep(.v-field__append-inner) {
padding: 0;
}
</style>
I don't think it matters, but the SFC component uses a Vuetify component (V-Select).