Hello theyounggun,
Regarding this feature, based on my experience, in new version of Outlook for Microsoft 365, this option is no longer available.
Instead, we can only share our calendar via modifying calendar permission: Share your Microsoft 365 or Outlook.com calendar with people inside or outside your organization.
By default, every internal user’s calendar opens free/busy permission to entire organization. If the recipient is internal user, you could try to add it in Outlook to see if you can see his free/busy time.
Regarding “Request Permission to view Recipient's Calendar” , I understand that this feature is very important to you, therefore recommend you to submit a feedback in Outlook UserVoice: https://outlook.uservoice.com/forums/322590-outlook-2016-for-windows?query=Request%20Permission%20to%20view%20Recipient%27s%20Calendar your time and understanding will be greatly appreciated.
Best Regards,
Anna