When you try to use the Plausible WordPress plugin on the WordPress playground, you get the following fatal error:

Fatal error: Uncaught RuntimeException: Plausible\Analytics\WP\Client\Lib\GuzzleHttp requires cURL, the allow_url_fopen ini setting, or a custom HTTP handler. in /wordpress/wp-content/plugins/plausible-analytics/src/Client/lib/Lib/GuzzleHttp/Utils.php:105 Stack trace:
#0 /wordpress/wp-content/plugins/plausible-analytics/src/Client/lib/Lib/GuzzleHttp/HandlerStack.php(49): Plausible\Analytics\WP\Client\Lib\GuzzleHttp\Utils::chooseHandler()
#1 /wordpress/wp-content/plugins/plausible-analytics/src/Client/lib/Lib/GuzzleHttp/Client.php(53): Plausible\Analytics\WP\Client\Lib\GuzzleHttp\HandlerStack::create()
#2 /wordpress/wp-content/plugins/plausible-analytics/src/Client.php(36): Plausible\Analytics\WP\Client\Lib\GuzzleHttp\Client->__construct()
#3 /wordpress/wp-content/plugins/plausible-analytics/src/Admin/Provisioning.php(40): Plausible\Analytics\WP\Client->__construct()
#4 /wordpress/wp-content/plugins/plausible-analytics/src/Plugin.php(42): Plausible\Analytics\WP\Admin\Provisioning->__construct()
#5 /wordpress/wp-includes/class-wp-hook.php(3): Plausible\Analytics\WP\Plugin->register_services('')
#6 /wordpress/wp-includes/class-wp-hook.php(3): WP_Hook->apply_filters(NULL, Array)
#7 /wordpress/wp-includes/plugin.php(2): WP_Hook->do_action(Array)
#8 /wordpress/wp-settings.php(2): do_action('plugins_loaded')
#9 /wordpress/wp-config.php(99): require_once('/wordpress/wp-s...')
#10 /wordpress/wp-load.php(2): require_once('/wordpress/wp-c...')
#11 /wordpress/wp-admin/admin.php(2): require_once('/wordpress/wp-l...')
#12 /wordpress/wp-admin/index.php(2): require_once('/wordpress/wp-a...')
#13 {main} thrown in /wordpress/wp-content/plugins/plausible-analytics/src/Client/lib/Lib/GuzzleHttp/Utils.php on line 105

With networking enabled, maybe allow_url_fopen should be true?

I've also filed an issue with Plausible who should catch this fatal error.