Hello @Courtney Regan !

I understand you need to block IPv6 for specific browsers and not on OS level

one suggestion is to use the Windows Advanced Firewall Rules

here is my example :

Create a new Outbound rule , Custom Rule , Select the exe file of the Browser and if you want the source or destination endpoints !

that simple!

Let me know if you need more details!

I hope this helps!

Kindly mark the answer as Accepted and Upvote in case it helped!

Regards