This is typical.  They don't want to have to support different Servers types. I ran these Unity modules with Ubuntu 18.0.4.  and didn't have any problems. I just made sure I had the correct Python version. You can always use Centos 8.4 or Rocky Linux if you don't want to use RHEL but want to make sure that you are supported.
Hello   I'm planning to start working on Ansible for Unity . in readme it shows only RHEL 8.4/8.5 supported for version 1.3.   Does anyone have tested on Ubuntu or Linux 7.x ?   Please share.  
Ansible for Dell Unity - Support Linux versions