Making a Preset with a LUT

I have UHD S-Log 3 files, and I'd like to make proxies with a REC 709 LUT.  I'm new to the proxy workflow, so I've been watching tutorials, and it looks simple.  I've made some test presets, without a LUT, and everything works.  But, I'd really like to have proxies that are closer in appearance to graded footage (I don't want to be looking at S-Log all day). 

When I try to make an encoding preset with a LUT, I'm able to add a Lumetri look, but when I try to select a non-Lumetri LUT from the dropdown menu, the window just closes. 

A few minutes ago, in a chat with Adobe tech support, I was told that this is impossible to do.  But, if it is, why do I find tutorials about doing it?  Any help would be greatly appreciated!