Just to be sure, did you download some strange version of the .iso from some non-official source? Or did you modify your Windows install in some way?
And you’re definitely selecting to install Windows 10 Pro, not something else?
I assumed you downloaded the generic .iso direct from Microsoft at https://www.microsoft.com/en-us/software-download/windows10 like most people do. (you can use the browser trick to get the page to give you .iso download options e.g. in Chrome I just hit F12, set the dimensions to something mobile looking, hit F5 to refresh the page, then go ahead & download the .iso)
The generic .iso is indeed a multi with the download option named “Windows 10 (multi-edition ISO)”, that itself doesn’t affect any of the steps above.
Then just use Rufus or similar to create a bootable USB with it.
You just need to select to “Domain join instead”, there is no need to actually go & set up an actual domain. See my other comment.
Hmm on the last few installs I’ve done (both Win 10 and 11) I just lead the installation to believe I’ll be doing a corporate/domain install & it always lets me create a normal user/password after that. Not necessary to unplug any ethernet/internet or anything of the sort.
It’s always worked for me both at work and at home.
Just to be sure, I spun up a virtual machine to install Windows 10 22H2, here are the steps I went through:
Done! You now installed Windows 10 Pro without a Microsoft Account.
Fastmail is great but it’s a totally different market /use case, you wouldn’t go with them if you’re privacy oriented. They’re better than Google in that sense but you’d go with Proton if you’re looking for privacy features.
Also keep in mind Fastmail is based in Australia and their government tends to be anti-privacy with the laws that get passed there.