Set email recipient based on value of select in freeform - possible?
FreeForm actually has a Dynamic Recipients field that sounds like it will do what you're wanting. I believe you can choose to have it displayed as a select field, radio buttons, or checkboxes.

Alternatively, you could probably create a little custom Twig and set up dynamic template notifications. I would think you should be able to switch the recipient array there based on the value of your select field for each submission (but it's possible I'm wrong; the Dynamic Recipients field definitely seems like the better option).