There have been a lot of questions raised on this, so I thought I would post an update here.
The current OctaneRender for Modo plugin supports Modo 13, 14 and 15 on Linux and Windows and is stable and robust, with builds for Octane 2020.2.3 and the latest Octane 2021.1.
On macOS there is an early build of the plugin for OctaneX (PR8), however it is Modo13 and 14 only (not Modo15). OctaneX is currently based on an earlier version of Octane (2020.1.5), and therefore an requires an older version of the Modo plugin code (from Sep 2020), which does not support Modo15. So the current Windows/Linux version of the Modo plugin is substantially more stable and complete than the OctaneX PR8 release of the plugin. I do not believe that this early OctaneX version of the plugin would be suitable for a studio doing production work - it is simply a proof-of-concept that the plugin will render with OctaneX.
OTOY have been working hard on OctaneX, and there is now PR13, which I understand is for M1 CPUs, and does not work with Intel CPUs. I have not been able to get OctaneX PR13 to render with the OctaneRender for Modo plugin on M1 hardware. I suspect that Modo would need to be compiled for M1, or to support Rosetta in order for this to work.
I think that a viable OctaneX version of the Modo plugin will happen when:
1) OTOY release an OctaneX build against the current version of Windows/Linux Octane (ie 2021.1 or 2022) so that Modo15 can be supported, and
2) OTOY enable support for Intel compiled binaries (such as Modo) on M1 hardware, OR Foundry release an M1 version, or a Rosetta-capable version of Modo15.
I hope that clears things up.
Thanks
Paul