1. Install with throwaway Microsoft account 2. Create new local admin account 3. Use local admin account to delete setup account
Not ideal, but not difficult either.
It's just that they've been hiding it more and more for consumer installations in successive releases.
Effectively, expect even enterprise to be online first with an escape hatch for those customers that need it, obviously only available on E5 or something like that...
I use https://rufus.ie/en/ when creating bootable USB sticks, and it turns out that this tool detects when you're trying to create a Windows installation medium, and prompts with a list of useful customizations, including "Remove requirement for online Microsoft account". (if you look through the screenshots on the webpage, there's one with the Windows customization dialog box)
However, as I mentioned below, I read something recently that says local account options are being removed in an upcoming version (I can't find the article now).
I presume it means the binaries are being removed from the ISO so this may no longer work (except for Enterprise and LTSC I'd imagine).
First you could still create a local account after there was backlash against cloud-everything, nowadays a local only Windows is quite complex to set up.
The Cortana/search bar stuff was also regularly re-enabled or parts of it made non-configurable, with them only occasionally backtracking. Not to speak of the ads that are included nowadays.
Their strategy generally seems to be boiling the frog when it comes to pushing these features onto the users, whether they want it or not.