I think this is a perfect use case for CentOS/RHEL as opposed to Ubuntu when the machine has only one job and nothing shall stand in its way, ie when you expect everything to be bug-for-bug compatible. But I fail to understand why a vendor of an MRI machine charging tens of thousands for installation/support cannot provide a supported RHEL OS which costs $180-350/yr in the cheapest config [1].
[1]: https://www.redhat.com/en/store/linux-platforms