The package system-config-samba is not available in debian, raspbian and probably some other variants. I believe it was added in ubuntu.
Shall I submit a pull request to install cifs-utils instead? Then the centos and debian roles install the same packages. cifs-utils is available since wheezy

I tested the role on 20.04, and got:

  TASK [geerlingguy.samba : Ensure Samba-related packages are installed (Debian).] ***
  failed: [instance] (item=['samba', 'samba-common', 'system-config-samba']) => {"ansible_loop_var": "item", "changed": false, "item": ["samba", "samba-common", "system-config-samba"], "msg": "No package matching 'system-config-samba' is available"}

[DEPRECATION WARNING]: Invoking "apt" only once while using a loop via squash_actions is
deprecated. Instead of using a loop to supply multiple items and specifying name: "{{ item }}",
please use name: ['samba', 'samba-common', 'python-glade2', 'system-config-samba'] and remove the
loop. This feature will be removed in version 2.11. Deprecation warnings can be disabled by
setting deprecation_warnings=False in ansible.cfg.

I am going to fix this by extracting the packages to a variable in its respective OS family file (Debian).
We can probably merge the two tasks for Debian and RedHat by extracting both to a variable and then using the generic package, but I am not in a position to test the RedHat changes.

It would be nice if I could add variables like:

samba_shares:
  - name: example
    options: |
      create mask = 0777
      directory mask = 0777

Something along those lines (at a minimum), and it would output in /etc/samba/smb.conf:

[example]
   create mask = 0777
   directory mask = 0777

(Just as an example).

CentOS 5 needs packages samba3x, samba3x-common and samba3x-winbind because the base samba packages are incompatible with cifs-utils.

I'm relatively new to Ansible, so bear with me if I'm missing some critical details that make my suggestion unworkable, BUT...

Attempting to use this role to manage Samba on an Ubuntu 20.04 server, I receive this error:

TASK [geerlingguy.samba : Ensure Samba-related packages are installed (Debian).] ***************************************
failed: [clus0-node0-apct11.local] (item=['samba', 'samba-common', 'python-glade2', 'system-config-samba']) => {"ansible_loop_var": "item", "changed": false, "item": ["samba", "samba-common", "python-glade2", "system-config-samba"], "msg": "No package matching 'python-glade2' is available"}

Further, if the reference to python-glade2 is removed from the task, a subsequent attempt also fails due to removal of the system-config-samba package. So, my educated guess is that these two packages have been removed from Ubuntu 20.04 completely.

The task works fine if I remove these packages and update the task to only install the samba package, allowing apt to resolve any other dependencies. I don't know whether the absence of python-glade2 will cause problems further down the line, however, so this may not be a workable solution to the problem?

How to create a samba user and give access to a specific folder ??

Is there a reason a task to start and enable NMB isn't included in this role?