Friends tab not visible in find my

You are indeed missing the People tab in the toolbar at the bottom of the screen. It should be to the left of "Devices".

iPhones sold in some asian countries (and perhaps others) do not have this functionality due to regulations. If you acquired your iPhone from such a country, you will not be able to have this functionality, even in your own country.

There is a red dot next to “Me” in the lower right. Tap there and resolve the issue at that tab.