For 10, unplug ethernet or do not connect to wi-fi and it should all you to continue or allow you to skip creating an MS account.
On the one system I use for gaming, before I install 10 which I have done a few times, I shutdown computer, physically unplug ethernet cable, then turn on computer and start the installation process, and I’ve created a local account everytime. Do not plug in cable or connect online until Windows has rebooted to the start desktop with Start menu. If you connect during installation it could force you to create online account.