Adding “Changelog” as a second tab to the auto updater custom plugin

I believe you have to add it into your plugin data array, see below:

$packages['plugin-slug'] = [
    'versions' => [
        '1.0.0' => [
            'name'              => 'WP Awesome Plugin',
            'version'           => '1.0.0',
            'new_version'       => '1.0.0',
            'date'              => '2023-02-10 14:17:00',
            'tested'            => '6.1.1',
            'package'           => 'https://127.0.0.1/plugin-slug-1.0.0.zip',
            //
            'author'            => '<a href="https://127.0.0.1/">Author</a>',
            'author_profile'    => 'https://127.0.0.1/',
            'homepage'          => 'https://127.0.0.1/wordpress-plugins/plugin-slug/',
            'requires'          => '5.8',
            'requires_php'      => '7.0',
            'description'       => 'This is an awesome plugin!',
            'short_description' => 'This is an awesome plugin!',
            'changelog' => 'Put your changelog here.'
        ],
    ],
    'info'     => [
        'url' => '',
    ],
];

Then, when you’re running through the output for your plugin updater:

if ( $action === 'plugin_information' ) {
    $data = new stdClass;

    $data->slug              = $args->slug;
    $data->name              = $latest_package['name'];
    $data->version           = $latest_package['version'];
    $data->new_version       = $latest_package['new_version'];
    $data->last_updated      = $latest_package['date'];
    $data->download_link     = $latest_package['package'];
    $data->tested            = $latest_package['tested'];
    //
    $data->author            = $latest_package['author'];
    $data->author_profile    = $latest_package['author_profile'];
    $data->homepage          = $latest_package['homepage'];
    $data->requires          = $latest_package['requires'];
    $data->requires_php      = $latest_package['requires_php'];
    //
    $data->description       = $latest_package['description'];
    $data->short_description = $latest_package['short_description'];
    $data->sections = [
        'description' => $latest_package['description'],
        'changelog'  => $latest_package['changelog'],
    ];

    print serialize( $data );
}

I think the changelog is supposed to be in the sections portion.