mobility sles12 sp2?

My Groupwise 2018 sp1. mobility servers are currently installed on Sles 12 sp2.  These are VMs that were originally Sles 11. What is my best path forward? Retire and leave it to someone else has come to mind

It looks like we should be on Sles 12 sp4 at a minimum. I didn't see any instructions of this in the documentation. If it's in there someplace please point me toward it.