I'm seeing a lot of very interesting answers but I'm wondering what you mean by "production environment".

Do you mean VFX Production? (English not my first language so if "production" is used in different industries, well, I didn't know).

I'm new to the industry and worked for small companies that don't use Linux. But my VFX peeps use Rocky, Mint, and Ubuntu ( stronger preference for Rocky in studios).

Most likely debian or debian-distroless

A company I worked at 2016-2022 used mainly CentOS and Ubuntu for all their servers at customers' sites

I always use Ubuntu Server. It was my first distro 20 years ago and it's still where I'm most comfortable.

I was working as a DWDM technician sometime ago and IIRC most of DWDM hardware (or at least the Infinera ones, as I had used those the most) were actually running on Gentoo, which was kinda surprising for me.

But in "regular" environments I have mainly seen Ubuntu or Debian.

I work for a big enterprise, we have RHEL on all our Linux servers save for a few that are SuSe for SAP.

My current job is all Ubuntu LTS, my job before that was all CentOS, and my job before that was a mixture of Debian and FreeBSD.

So what are the biggest differences. Or is it mostly the same? Also thanks for the responses!

Mostly cost. We used to run a lot of Oracle databases and they have become extremely expensive to keep running. So we are migrating to PostgreSQL. The servers were getting migrated to CentOS but now that RedHat fucked that distro we are going back to RedHat. Part of that deal is switching from chef to Ansible. So to save costs we are consolidating to a single vendor.

I think Ubuntu is the most popular distro in the cloud, at least based on cloud provider metrics. Dockerhub shows like 30 million downloads a week for it regularly, which is a lot compared to most images. Debian would be good to learn as that's what Ubuntu is based on and all the major software with will probably target it. Alpine is good to learn as it's super slim, tends to be used for containers a lot.

For learning system administration, I think Cent OS Stream can be a great choice. Not because it offers something special than others but because it would familiarize you with the RHEL/Fedora family and in my experience majority of enterprise-servers are using one of its family members, be it RHEL, the former CentOS, Oracle Linux, Amazon Linux or some other variant.

At work: Alpine-based docker containers. Flatcar Container Linux for host VMs.

Personally: Ubuntu Server. Some alpine docker containers.