As it says in the FAQ at https://wordpress.org/plugins/jonradio-multiple-themes/faq/
Will this plugin work with Paid Themes?
With the massive rewrite of Theme Selection logic in Version 5 of this plugin, it should now work with all Paid Themes and Plugins. But we have only tested the few Paid Themes whose authors have provided us with permission to use, without charge, their themes for test purposes. Elegant, for example, allows us to accept copies of its Themes provided by its customers who require assistance with the jonradio Multiple Themes plugin. On the other hand, some other Paid Theme authors have simply ignored our requests, despite our stated willingness to sign a non-disclosure agreement.
We do encourage you to contact us if you run into problems when using the jonradio Multiple Themes plugin with a Paid Theme, as the problem may not be unique to the Paid Theme.
To state the obvious, the cost of purchasing a license for all Paid Themes for testing purposes is prohibitive for an Open Source plugin such as this one.
The guarantee needs to come from the people you buy the Paid Themes from, since they are the only ones who can refund your money if things don’t work out.
I should also mention that the homepage as one theme and rest of the site as another theme ideally fits into the Subdirectory approach to WordPress Multisite, which would eliminate your requirement for this plugin altogether, since WordPress allows different Themes for different Sites in a Multisite (“Network”) installation.
Finally, I need to make it clear that David currently provides the official support for this plugin. These are just my comments on the subject.
I agree completely with Jon. Multiple Themes is a very cool plugin, but you’re crossing the beams, so use it carefully.
If you’re buying themes now, my recommendation is to search for one theme that can do it all. Don’t settle until you find it.
–David
P.S. Marking as resolved because sage advice has been provided.
