Hello Matteo. Unfortunately, you cannot turn on NDI technology in Microsoft Teams without an administrator account, this feature requires updating meeting policies in the Teams Admin Center which is limited to admin users. Without admin access, NDI will not appear in your Teams settings nor will you be able to turn it on or use it.
Here's the reference: Allow broadcast production in Teams meetings with NDI and SDI hardware Broadcasting audio and video from Microsoft Teams with NDI and SDI technology
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Best regards,