It really depends. I work for a large company and we use Ubuntu, Oracle, RedHat, and SLES. We were moving from Oracle to Ubuntu but now we are going back to RedHat.
Currently we deploy like this: Ubuntu: PostgreSQL, web servers, some engineering workstations, and big data Oracle & RedHat: web servers, security applications, and network systems
So just having a fundamental understanding of Linux and you will be fine SUSE: SAP and HR software