In the install section for linux, there should be a section for RHEL users to install openal-soft before using Classicube, otherwise audio won't work (curl is installed by default on RHEL, or at least Rocky Linux (that is the distribution i am using - please double-check)). An example would be a command like
$ sudo dnf install openal
or
$ sudo dnf install openal-soft
(Both will work)