Cloud xxx belongs to eu geo, please access via api-eu.cloudinary.com, issue with free Cloudinary European account

I am running in the following error when uploading a picture to the Media Library:

{
  message: 'Cloud xxx belongs to eu geo, please access via api-eu.cloudinary.com',
  name: 'Error',
  http_code: 400
}

I have tried adding the following settings to env/production/plugin.ts

export default ({ env }) => ({
  upload: {
    config: {
      provider: "cloudinary",
      providerOptions: {
        cloud_name: env("CLOUDINARY_NAME"),
        api_key: env("CLOUDINARY_KEY"),
        api_secret: env("CLOUDINARY_SECRET"),
        upload_prefix: "https://mo-api-eu.cloudinary.com",
      },
      actionOptions: {
        upload: {},
        uploadStream: {},
        delete: {},
      },
    },
  },
});

Supposedly the upload_prefix option should be changed to mo-api-eu.cloudinary.com as suggested here https://support.cloudinary.com/hc/en-us/community/posts/4417951840018-Media-Optimizer-API-Cloud-name-here-belongs-to-eu-geo-please-access-via-api-eu-cloudinary-com.

This instead will lead to the error:

{
  message: 'Server returned unexpected status code - 403',
  http_code: 403,
  name: 'UnexpectedResponse'
}

If I try upload_prefix: "https://xxx.mo.cloudinary.net", because my Optimization profile name is xxx`, I get the error:

{
  message: 'Server returned unexpected status code - 403',
  http_code: 403,
  name: 'UnexpectedResponse'
}

Has anyone been able to set it up correctly a free Cloudinary account based in Europe?