Comment by KingOfLechia
3 months ago
Even if you try to install it using a flash drive, it still asks you to connect to the internet to "verify" the installation. https://sneak.berlin/20201204/on-trusting-macintosh-hardware... explains how it's ensured on the firmware level that you really connect with Apple servers.
That is if you have a completely new machine or have zerod out the disk.
If you are simply re-installing the OS then you can do it without internet.