You can overwrite the default provider template. Just add the template property with the path to the .hbs template inside your provider config.

remark: {
  plugins: [
    [ '@noxify/gridsome-plugin-remark-embed', {
        'enabledProviders' : ['Youtube', 'Twitter', 'Gist'],
        'Youtube' : {
            template: './src/providerTemplates/Youtube.hbs',
        },
        
    }]
  ]
}

Behind the scenes, we're using path.resolve() to get the absolute path the example path is based on your project route like the baseDir from the @gridsome/source-filesystem