Maybe this is not really an issue, when I exported a Rule Machine Legacy rule, the generated JSON has a glitch: The array itself is being specified as a string. Maybe, the importer handles it -- I have not tried to import the rule, yet -- but thought I'd let you know.
My hub details are:
Also, I didn't see a "Bug Report" category in this forum. So please let me know if I should have posted it to a different category.