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Microsoft is plugging more holes that let you use Windows 11 without an online account
(www.theverge.com)
This is a most excellent place for technology news and articles.
Here's your bypass:
In OOBE, go through MS account creation. Tell it you were born today. It'll let you set a password for the MS account before rejecting you due to COPA requirements. At this point, you can make an offline account without having even created an MS account, let alone having to use one.
This will not go away - it's a legal thing. MS doesn't want to deal with COPA stuff for very young kids, so this flow exists. Enjoy.
What if they just ask your age as step 1 of the setup?
Same thing, that doesn't change anything.