You may have already seen this discussion on stack overflow. https://stackoverflow.com/a/60188132I don't know enough javascript to try it out.
Absolutely make a backup before unzipping, importing, saving, and reloading with the attached file. I am definitely out of my depth! You will probably need a modern (e.g. Chrome, Firefox) browser. This is not a universal solution (only adds Kannada), and there may be tweaks that need to be done (or actually undone) re case folding.
But it did appear to work – you can see the faint Kannada characters in this screen grab:
