It's not immediately clear whether your are referring to the enterprise server, HTML server, etc, or all of them.
However, My Oracle Support Doc ID 747323.1 has the last known set of MTRs for pre- EnterpriseOne 9.1 releases for all components. But, as expected, it is rather old. For example, Windows 2008 is listed as the OS for Windows enterprise servers - which obviously is not supported by Microsoft anymore.
You may have to go to a third party for support or consider bumping up to a supported release if possible.