Hello anispwyn,
Welcome to the Samsung Developer forum!
Based on the TV model number, you have a 2024 TV and access to developer mode has changed.
On a 2024 Samsung Smart TV,
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Open Smart Hub
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In the top banner, click Apps
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Find and click Settings (probably at or near the bottom of the page)
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Use the remote to enter 12345
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From the pop-up window, you can enable or disable developer mode
For TV models earlier than 2024, see this page, TV Device, for more information.