This assumes that you have the folders for the switching prepared, and you want to verify that it works.
- Make sure that the templates in the various folders have something different - it can just be a note or something - to ensure you can tell which one you are seing.
- Set the page theme to a theme that has one of the desired CSS-Frameworks and reload the page. You should now see that the correct output was generated.
- Set the page theme to another theme targeting another framework - you should see that it works.
Troubleshooting
If you keep seing the same same output you usually made one of these mistakes:
- Your templates are so similar that you can't tell which one was loaded
- Your templates don't have matching names (that's required)
- Your theme doesn't have a koi.json, so it doesn't publish what CSS-framework it's using
If all else fails, look at the insights. You should see entries about Polymorph - search for these to see what the engine was doing.