iOS 15 moved the address bar to the bottom for easier reachability. If you want it back at the top, you can press the two AAs in your address bar and select: "Show Top Address Bar."
How to Move the address bar to the top again
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How to Customize new tab
You can customize how your browser looks when you open a new tab!
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9 Safari Features and Tips for iPhone
How to use Safari tab management, reader mode, pinned tabs, and customize the browser on iPhone