If you changed "text_translated.lua" directly into your installed game folder and launch the LocJAM edition from the itch.io app, you can play your localized version. (Or at least, it works on my computer)
This is not a very safe way to go because you are handling files "live" here, but if you have made backups, you should not have any issue. Worst case scenario, if the game breaks, you can simply copy your translation elsewhere, delete+reinstall the LocJAM edition from the itch.io app, and start messing around in the folder again ;)
Then when you want to upload your version to the jam, simply zip *a copy of* the LocJAM edition folder (from which you might have to remove the hidden ".itch" folder), change its name, and you are theoretically good to go.