I am also using Office 2021 and have just added the Camera button in Quick Access Toolbar following the steps in post #2 by AskMeAboutExcel. You may have missed out some steps.

In any case, without the Camera button, you can still paste linked picture by following these steps: Select the range you want to link as picture > Ctrl+C to copy > right-click on any cell outside the range > click on ">" at Paste Special > Other Paste Options > Linked Picture (I).