add Ubuntu detection fallback
Some Ubuntu flavors apparently don't have UBUNTU_CODENAME set. WSL seems to be such a case. However, it's still preferable to use it if possible to allow proper version detection for Ubuntu derivates.
Self sign-up has been disabled due to increased spam activity. If you want to get access, please send an email to a project owner (preferred) or at gitlab(at)nic(dot)cz. We apologize for the inconvenience.
Some Ubuntu flavors apparently don't have UBUNTU_CODENAME set. WSL seems to be such a case. However, it's still preferable to use it if possible to allow proper version detection for Ubuntu derivates.