Hey ​@soumyaux , good news! This has now been implemented 

Figma Sites now supports apex domains and custom subdomains, so you now have more options for personalizing your URL.

• Apex domain: Connect root domains (like example.com) to your Figma Site, with optional redirects between apex domains and www subdomains.
• Custom subdomain: Personalize your URL like yourname.figma.site and make it easier to integrate with any existing domains.

You can learn more about setting up your new domains in Figma Sites here.