disable media wordpress and use the browser file uploader to upload - php

Question

I use the One User Avatar plugin, Inside the settings, there is a check box with the title "Always use the browser file uploader to upload avatars". I tick it. But when I try to change the default avatar, it still uses WordPress media, I came across the following code in the file below :
path : /plugins/one-user-avatar/includes/class-wp-user-avatar-admin.php
public function wpua_add_default_avatar() {
global $avatar_default, $mustache_admin, $mustache_medium, $wpua_avatar_default, $wpua_disable_gravatar, $wpua_functions;
// Remove get_avatar filter
remove_filter( 'get_avatar', array( $wpua_functions, 'wpua_get_avatar_filter' ) );
// Set avatar_list variable
$avatar_list = '';
// Set avatar defaults
$avatar_defaults = array(
'mystery' => __( 'Mystery Man', 'one-user-avatar'),
'blank' => __( 'Blank', 'one-user-avatar'),
'gravatar_default' => __( 'Gravatar Logo', 'one-user-avatar'),
'identicon' => __( 'Identicon (Generated)', 'one-user-avatar'),
'wavatar' => __( 'Wavatar (Generated)', 'one-user-avatar'),
'monsterid' => __( 'MonsterID (Generated)', 'one-user-avatar'),
'retro' => __( 'Retro (Generated)', 'one-user-avatar')
);
$avatar_defaults = apply_filters( 'avatar_defaults', $avatar_defaults );
// No Default Avatar, set to Mystery Man
if ( empty( $avatar_default ) ) {
$avatar_default = 'mystery';
}
// Take avatar_defaults and get examples for unknown#gravatar.com
foreach ( $avatar_defaults as $default_key => $default_name ) {
$avatar = get_avatar( 'unknown#gravatar.com', 32, $default_key );
$selected = ( $avatar_default == $default_key ) ? ' checked="checked" ' : '';
$avatar_list .= sprintf(
'<label><input type="radio" name="avatar_default" id="avatar_%1$s" value="%1$s" %2$s/> ',
esc_attr( $default_key ),
$selected
);
$avatar_list .= preg_replace( "/src='(.+?)'/", "src='\$1&forcedefault=1'", $avatar );
$avatar_list .= ' ' . $default_name . '</label>';
$avatar_list .= '<br />';
}
// Show remove link if custom Default Avatar is set
if ( ! empty( $wpua_avatar_default ) && $wpua_functions->wpua_attachment_is_image( $wpua_avatar_default ) ) {
$avatar_thumb_src = $wpua_functions->wpua_get_attachment_image_src( $wpua_avatar_default, array( 32, 32 ) );
$avatar_thumb = $avatar_thumb_src[0];
$hide_remove = '';
} else {
$avatar_thumb = $mustache_admin;
$hide_remove = ' class="wpua-hide"';
}
// Default Avatar is wp_user_avatar, check the radio button next to it
$selected_avatar = ( 1 == (bool) $wpua_disable_gravatar || 'wp_user_avatar' == $avatar_default ) ? ' checked="checked" ' : '';
// Wrap WPUA in div
$avatar_thumb_img = sprintf( '<div id="wpua-preview"><img src="%s" width="32" /></div>', esc_url( $avatar_thumb ) );
// Add WPUA to list
$wpua_list = sprintf(
'<label><input type="radio" name="avatar_default" id="wp_user_avatar_radio" value="wp_user_avatar" %s /> ',
$selected_avatar
);
$wpua_list .= preg_replace( "/src='(.+?)'/", "src='\$1'", $avatar_thumb_img );
$wpua_list .= ' ' . __( 'One User Avatar', 'one-user-avatar' ) . '</label>';
$wpua_list .= '<p id="wpua-edit"><button type="button" class="button" id="wpua-add" name="wpua-add" data-avatar_default="true" data-title="' . __( 'Choose Image', 'one-user-avatar' ) . ': ' . __( 'Default Avatar', 'one-user-avatar' ) . '">' . __( 'Choose Image', 'one-user-avatar' ) . '</button>';
$wpua_list .= '<span id="wpua-remove-button"' . $hide_remove . '>' . __( 'Remove', 'one-user-avatar' ) . '</span><span id="wpua-undo-button">' . __( 'Undo', 'one-user-avatar' ) . '</span></p>';
$wpua_list .= '<input type="hidden" id="wp-user-avatar" name="avatar_default_wp_user_avatar" value="' . $wpua_avatar_default . '">';
$wpua_list .= '<div id="wpua-modal"></div>';
if ( 1 != (bool) $wpua_disable_gravatar ) {
return $wpua_list . '<div id="wp-avatars">' . $avatar_list . '</div>';
} else {
return $wpua_list . '<div id="wp-avatars" style="display:none;">' . $avatar_list . '</div>';
}
}
How can I disable WordPress media and choose and upload a file from my computer?
I found the following code :
$wpua_list .= '<p id="wpua-edit"><button type="button" class="button" id="wpua-add" name="wpua-add" data-avatar_default="true" data-title="' . __( 'Choose Image', 'one-user-avatar' ) . ': ' . __( 'Default Avatar', 'one-user-avatar' ) . '">' . __( 'Choose Image', 'one-user-avatar' ) . '</button>';
I replaced it with the following code :
$wpua_list .= '<p id="wpua-edit"><input name="wpua-file" id="wpua-file" type="file"><button type="submit" class="button" id="wpua-upload" name="wpua-upload" data-avatar_default="true" data-title="' . __( 'Upload', 'one-user-avatar' ) . ': ' . __( 'Default Avatar', 'one-user-avatar' ) . '">' . __( 'Upload', 'one-user-avatar' ) . '</button>';
But when I go to wp-admin/options-discussion.php address and select and upload a photo from the computer, nothing is uploaded.
Where am I doing wrong? Thank you for taking the time to read my question.