Redhat and Passenger migration options?

We have a Rails application that runs via an old Apache using Passenger on an old release of RedHat Linux.

What are the logical options to avoid binary compatibility issues when moving to a newer RedHat Linux?

Not sure what you meant regarding binary compatibility issues moving to a new version of RHEL. But if you are moving to or upgrading RHEL I’d definitely suggest switching to Nginx/Passenger as Nginx benchmarks much better than Apache does and the passenger integration is much more straight forward than Apache. If you have specific questions, please drop them here.