Now CDH 6.2 supports Ubuntu 18.40. Will CDH 5 also going to support Ubuntu 18.04?
No, it is not supported. Please check our documentation for more information. About the supported OS details
CDH 6.2.x and 6.3.x supports 18.04 LTS (Bionic).
If you would like more information about Ubuntu 18.04 support for CDH 5, please contact your account team. Thanks