If you do accidentally connect to a network, before you realise this, there's no way to get it to forget. Rebooting doesn't work. The only solution I found was walking 30m away to the other side of the parking lot out of range of WiFi.
Start the install over from scratch. You can have wifi enabled when installing. Just don't plug in a network cable and don't connect to a wifi network when it prompts you to. Read carefully, you can avoid connecting and if you do you don't connect, you don't have to use a Microsoft account.
Shift+F10 is your friend at installation time.
Disable WiFi in the BIOS.
Insane that you have to resort to that.
Re:Microsoft announces Windows 11
by garethrowlands on Thursday June 24, 2021 @06:54PM
(#27624974)
You don't have to resort to that.
I do it all the time. Do not plug network cable and do not connect to WiFi. Windows then proceeds to setting up local account