Themes

The settings page just needs extra settings for the language based parts - the title and the text of the warning, something like below (note Essential2 is my clone of essential for testing things like this out - you would need your own theme name and also I've used Welsh as my alternate language, you would use whatever other language packs you are using on your site - I've left the English one unchanged, but you could edit that for clarity.

You would then need to add the necessary strings to the language files in the theme/lang/en and theme/lang/cy (for Welsh, replace with your language pack). You would also need to do this for the other two Alert setting groups in the settings.php file of your theme.

That should create the settings and I'll give you the correct code to use it in the layout files (and hopefully full code for this and a language page and instructions) tomorrow, if Mary doesn't beat me to it, being the night bird she sometimes is

    //This is the descriptor for Alert One
    $name = 'theme_essential2/alert1info';
    $heading = get_string('alert1', 'theme_essential2');
    $setting = new admin_setting_heading($name, $heading, $information);
    $temp->add($setting);
    
    // Enable Alert
    $name = 'theme_essential2/enable1alert';
    $title = get_string('enablealert', 'theme_essential2');
    $description = get_string('enablealertdesc', 'theme_essential2');
    $default = false;
    $setting = new admin_setting_configcheckbox($name, $title, $description, $default, true, false);
    $setting->set_updatedcallback('theme_reset_all_caches');
    $temp->add($setting);
    
    // Alert Type.
    $name = 'theme_essential2/alert1type';
    $title = get_string('alerttype' , 'theme_essential2');
    $description = get_string('alerttypedesc', 'theme_essential2');
    $alert_info = get_string('alert_info', 'theme_essential2');
    $alert_warning = get_string('alert_warning', 'theme_essential2');
    $alert_general = get_string('alert_general', 'theme_essential2');
    $default = 'info';
    $choices = array('info'=>$alert_info, 'error'=>$alert_warning, 'success'=>$alert_general);
    $setting = new admin_setting_configselect($name, $title, $description, $default, $choices);
    $setting->set_updatedcallback('theme_reset_all_caches');
    $temp->add($setting);
    
    // Alert Title.
    $name = 'theme_essential2/alert1title';
    $title = get_string('alerttitle', 'theme_essential2');
    $description = get_string('alerttitledesc', 'theme_essential2');
    $default = '';
    $setting = new admin_setting_configtext($name, $title, $description, $default);
    $setting->set_updatedcallback('theme_reset_all_caches');
    $temp->add($setting);
    
    // Alert Text.
    $name = 'theme_essential2/alert1text';
    $title = get_string('alerttext', 'theme_essential2');
    $description = get_string('alerttextdesc', 'theme_essential2');
    $default = '';
    $setting = new admin_setting_configtextarea($name, $title, $description, $default);
    $setting->set_updatedcallback('theme_reset_all_caches');
    $temp->add($setting);

    // Alert Title - Welsh.
    $name = 'theme_essential2/alert1title_welsh';
    $title = get_string('alerttitle_welsh', 'theme_essential2');
    $description = get_string('alerttitledesc_welsh', 'theme_essential2');
    $default = '';
    $setting = new admin_setting_configtext($name, $title, $description, $default);
    $setting->set_updatedcallback('theme_reset_all_caches');
    $temp->add($setting);
    
    // Alert Text.
    $name = 'theme_essential2/alert1text_welsh';
    $title = get_string('alerttext_welsh', 'theme_essential2');
    $description = get_string('alerttextdesc_welsh', 'theme_essential2');
    $default = '';
    $setting = new admin_setting_configtextarea($name, $title, $description, $default);
    $setting->set_updatedcallback('theme_reset_all_caches');
    $temp->add($setting);

Odd.  Time for a Shoelace proof of concept.