This camera model recently released in last 2 months with new processor vs. previous model. LR release history shows G9X support added in standalone version 6.3. When will support for raw file import be available for newer G9X Mark II?
Somewhat related: I have previously upgraded LR to standalone ver 5.7. When I do upgrade to this new release is it best practice (to remove all unnecessary files except cat) to uninstall 5.7, then fresh install 6.x trial then use serial no. from 5.7?
The G9X MkII will probably been supported with the next dot release - Adobe does not say when they will release it.
If you install a new version (i.e. Lr5 to 6) then the existing installation will be left untouched. You can have both running. The catalog will be copied and upgraded. However, the upgraded catalog can no longer be opened with the old version.
Usually, after a few days/weeks of stable work with the new version, the old can be deleted/removed.