PHP 8.0 alpha3 was released 23 july and netcurl has been tested together with this release. It turns out that a few changes has been made in the core of curl that enforced a minor patch in netcurl for it to work properly again. In short, it is about how curl is presenting itself in v8.0, which is no longer as a resource. It instead returns objects on curl_init, generating a CurlHandler, CurlMultiHandler, etc.
You can read about the change at https://github.com/php/php-src/blob/php-8.0.0alpha3/UPGRADING while waiting for the upgrade.
The Bamboo test suite now also includes PHP 8 tests, starting with PHP 8.0alpha3.