From the Centos list:

Wed 27/01/2021 13:20
From Anton
To: [log in to unmask]
Centos-6 compatible packages are available from the official sudo
webpage. It's a later version of sudo and I'm not sure if that will
cause problems. I've tried installing it and so-far so-good.

https://urldefense.proofpoint.com/v2/url?u=https-3A__www.sudo.ws_download.html&d=DwIGaQ&c=gRgGjJ3BkIsb5y6s49QqsA&r=gd8BzeSQcySVxr0gDWSEbN-P-pgDXkdyCtaMqdCgPPdW1cyL5RIpaIYrCn8C5x2A&m=4gViHxlwEReiAMmwLMsOU_aWN247JhtKzgVS3Dwo2ec&s=f8ncxn_x8nNK-vZ5uqfNS-VwrQaFRmW37iYXZwDIpYE&e= 

# End quote.

It has worked on the small number of SL6 systems I have.
Rhys