In the RHEL-compatible area, RHEL7 and CentOS7 are currently supported. Both are a bit outdated and I would not like to set them up for new deployments.
RHEL8 is not yet officially supported and CentOS8 is no longer an option as the distro has changed direction to being an upstream build of RHEL8. Rocky Linux could be a good alternative, we have had very good experiences with it.
We don't need to talk about SLES 12, that's so old....
And for Windows Server (I would never use that, but many companies do), 2016 is the last supported version. 2019 has been around for 3 years, 2022 is coming this fall.
So please support more recent operating systems, preferably free ones too!