Hi there!

Thanks for your query.

Would you please describe it more?

However, you can use multiple templates in a single Joomla site:

https://www.joomshaper.com/blog/how-to-use-two-or-more-templates-in-one-joomla-site

And you can have a look into this one too to see if it helps!

https://docs.joomla.org/Multiple_Domains_and_Web_Sites_in_a_single_Joomla!_installation

If they doesn't serve your answer, you may ask on Joomla forum as it seems all about Joomla.

Best Regards