16.2.8 Linux preview pass type is not populated
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Before posting a bug report, please check the following:
1. That the issue has not already been disclosed
2. That the issue is specific to this plugin, and not Octane in general (Try reproducing it in Standalone)
Bugs related to the Octane Engine itself should be posted into the Standalone Support sub-forum.
All bug reports should include the information below, along with a detailed description of the issue and steps to reproduce it.
A. Operating System, including version (i.e. Win 7, OSX 10.11.2, Ubuntu 14.04, etc.)
B. Graphics Card(s) model (i.e. GTX 580 - 3GB, TITAN, etc.)
C. RAM Capacity (i.e. 6 GB)
D. Nvidia driver version (i.e. 7.50, 7.5.22)
E. OctaneRender Standalone version, if installed (i.e. 2.24.2, 2.23, etc.)
F. OctaneRender plugin version (i.e. v2.25 - 2.21)
G. Host application version, including build number if available (i.e. 3ds Max 2016 Build 18.0)
Before posting a bug report, please check the following:
1. That the issue has not already been disclosed
2. That the issue is specific to this plugin, and not Octane in general (Try reproducing it in Standalone)
Bugs related to the Octane Engine itself should be posted into the Standalone Support sub-forum.
All bug reports should include the information below, along with a detailed description of the issue and steps to reproduce it.
A. Operating System, including version (i.e. Win 7, OSX 10.11.2, Ubuntu 14.04, etc.)
B. Graphics Card(s) model (i.e. GTX 580 - 3GB, TITAN, etc.)
C. RAM Capacity (i.e. 6 GB)
D. Nvidia driver version (i.e. 7.50, 7.5.22)
E. OctaneRender Standalone version, if installed (i.e. 2.24.2, 2.23, etc.)
F. OctaneRender plugin version (i.e. v2.25 - 2.21)
G. Host application version, including build number if available (i.e. 3ds Max 2016 Build 18.0)
When rendering images or animations you should be able to save the pass you want (especially denoised renders) to output files. This is usually controlled by the "Preview Pass Type" setting in the "Render Layers" panel. The problem is that the plugin doesn't populate the Octane passes in the dropdown menu so you can't select which pass you would like to output.
Linux Mint 21.3 x64 | Nvidia GTX 980 4GB (displays) RTX 2070 8GB| Intel I7 5820K 3.8 Ghz | 32Gb Memory | Nvidia Driver 535.171
Isn't preview pass for preview not for final rendering?
CPU – i9 13900KF, 128GB RAM, GPU – RTX 4090
System – Windows 11
My Behance portfolio, Blender plugin FB support group
System – Windows 11
My Behance portfolio, Blender plugin FB support group
It probably started out that way, but with Cycles you can also use it for Render (F12) and Animation (at least as far as I understand). Like a lot of things in Blender, sometimes it's hard to determine what does what. 
Linux Mint 21.3 x64 | Nvidia GTX 980 4GB (displays) RTX 2070 8GB| Intel I7 5820K 3.8 Ghz | 32Gb Memory | Nvidia Driver 535.171