This link is for Instructions and a link to the Request form to Unlink a Device :
How to Submit a Wallet Unlinking Request
Detailed Instructions with Screenshots below:
How to Remove Verified Devices (screenshots)
This Help Center article explains about linking limits.
How many Brave Rewards wallets can be linked to my crypto custodian account?
Brave is removing linking limits. Hopefully soon. You can track the issue here:
Implement solution for linking limits #18572