In this example, the update is blocked for Akismet and Classic Editor, but it can be used with any plugin. Don’t do this unless you have no alternatives.

/**
 * Block some plugins from updating
 *
 * @param array $parsed_args
 * @param string $url
 *
 * @return array
 * @throws JsonException
 */
function wporg_block_update_specific_plugins( $parsed_args, $url ) {

$blocked_plugins = [
'akismet/akismet.php',
'classic-editor/classic-editor.php',
];

if ( isset( $parsed_args['body']["plugins"] ) ) {
$plugins = json_decode( $parsed_args['body']["plugins"], true );

if ( isset( $plugins['plugins'] ) ) {
$installed_plugins = $plugins['plugins'];

foreach ( $blocked_plugins as $p ) {
unset( $installed_plugins[ $p ] );
}

$parsed_args['body']['plugins'] = json_encode( [ 'plugins' => $installed_plugins ], JSON_THROW_ON_ERROR );
}
}

return $parsed_args;
}

add_filter( 'http_request_args', 'wporg_block_update_specific_plugins', 5, 2 );