Enterpise espeically banking need standard and certification for reliability thats why , also certain Linux distro had certified before from China based on RHEL.

This is UNIX 03 certified OS with OSS alternatives from I gathered on internet :

- Apple OS X 10.7 - Apple macOS 26 , provide OSS Darwin 9 - Darwin 26

- Oracle Solaris 10 / 11 , provide OSS OpenSolais , then Illumos

- EulerOS 2.0 , based on RedHat Enterprise Linux / RHEL 7 and 8

- Inspur K-UX 2.0 , based on RedHat Enterprise Linux / RHEL 5

- Inspur K-UX 3.0 , based on RedHat Enterprise Linux / RHEL 7