In your notes you say you resolved the issue of not being able to select a custom LUT for encoding for a clip. In 12.1.2, you can now actually choose the LUT file you want. Unfortunately, while the preview window shows the LUT, the LUT option dialog box still says "Select..." When I render the file, the LUT is still not applied. Please have engineering look at this.
Hmmmm. I tried it out and it indeed happened to me too. I have filed a bug report.