Since October 27, 2022 the YouTube app for the Wii U has been discontinued and the app can no longer be accessed.
To check if the service is available the YouTube app requests a service token from https://account.nintendo.net/v1/api/provider/service_token/ with a YouTube specific client id.
This endpoint now responds with:

<errors>
    <error>
        <code>0123</code>
        <message>Service has expired</message>
    </error>
</errors>

The app then checks if acquiring this token has been sucessful and if not it will display the error. The acquired token itself is not used.
This is a Wii U Plugin System plugin for Aroma which just makes this request always return sucess and thus allowing the YouTube app to continue functioning.

On November 1st, 2022 YouTube started returning response 404 for the WiiU useragent platform.
Since v2.0 this plugin patches the platform in the useragent for the YouTube app to NoU instead of WiiU, which bypasses this block.

@ashquarky for the awesome patcher framework which was taken from Nimble.

# Build docker image (only needed once)
docker build . -t givemiiyoutube_builder

# make 
docker run -it --rm -v ${PWD}:/project givemiiyoutube_builder make

# make clean
docker run -it --rm -v ${PWD}:/project givemiiyoutube_builder make clean