Hi, @Brandon Ho
Thank you for posting in Microsoft Q&A forum.
We add SkipProductKey=YES to the customsettings.ini should work for some version, but some versions will always prompt for a key.
You may try to extract the Product key and then add SkipProductKey=YES and ProductKey=THE-KEY-I-EXTRACTED to the customsettings.ini to see if it helps.
For the reference:
https://www.reddit.com/r/MDT/comments/a1fpan/skip_its_time_to_enter_the_product_key/
https://www.reddit.com/r/MDT/comments/63twma/skip_product_key/
(Third-party link, just for your reference)
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