Hello,
I just had the same issue with installing voukoder. But I found a technical documentation in my DaVinci Resolve 18.6.6 installation that shows detailed information about structure and installing of plugins.
The .bundle file can be copied manually into this place
After (re)starting Davinci, voukoder is shown in the Export Video drop down list.
direct path to documentation: C:\ProgramData\Blackmagic Design\DaVinci Resolve\Support\Developer\CodecPlugin
OR open via DaVinci and select "CodecPlugin"
Hope this helps.
stefan