GIMP has functions similar to Photoshop, but it may not have all the advanced features that you need**. The user interface is different (I think better), so it takes some getting used to.
If you are going to use RHEL, then be sure to buy a support subscription---otherwise get Fedora or CentOS (if you really like a RedHat type system.
**For me GIMP does everything I need. IMHO, most Photoshop users do not NEED the advance features.