I tried installing Demo version for Maya 2020.4 but I am getting some errors when I launch Maya after installing Ornatrix.
"The procedure entry point AiArraySetVec2 could not be located in the dynamic link library C:\ProgramFiles\Ephere\OrnatrixMaya2020\Plug-ins\procedurals\Ephere.Ornatrix.ArnoldProcedural7.1.dll."
Please refer to this page for the MtoA versions supported by Ornatrix: https://ephere.com/plugins/autodesk/maya/ornatrix/docs/4/Arnold_Compatibility.html