Not so. You need an internet connection to download the Windows 11 ISO file. You have that. You need a Flash drive to house the ISO file. If you don't have one you can buy one cheaply. You need some instruction on how to to keep the installation from detecting the lack of things a normal Win 11 wants to see. You can find these instructions on elevenforum.com. The ISO file can be used for an upgrade or a clean installation. The ISO file doesn't care whether or not you are connected to a LAN. There is no cost for any of this other than buying a flash drive if you don't have one. Any machine running windows 10 can be upgraded to windows 11 regardless of age.
Not sure what you are trying to accomplish here. Of course you need an internet to download an ISO file, you need internet to download any file
I am very familiar on how to install windows from an ISO file. Since all my PC's are typically new builds, that's pretty much how I do it every time as I just buy the license key. I had a 256GB USB 3.0 Drive that had my ISO file which Installed from. As far from instruction from elevenforum, I didn't find that specific site, but there are many You tube videos that had a solution that didn't work. They had you go into the command prompt. I figured it out the hard way. My point is that windows, by default does not let you install w/o a network connection, so unless you have experience, or sites like elevenforumn.com it is not an easy process.
In addition, I never said that any computer running windows 10 can't be upgraded to 11. My point is that if you are doing a typical upgrade vs a clean install, the network drivers should already be there. In many cases, the network drivers will be auto detected during the install process. I am guessing here, but I assume since my network chipset is much newer 10G Ethernet, which may be why it could not be detected.
Granted my install was much more complicated because the only other PC I have is a MacBook Pro. I had to install Parallels and Windows (30 day trial), so I could even get the ISO set up for my new PC build. Even worse the Macbook only has USB Type C connections, I did not have an adapter, but I did have an open port in my docking station, so solved that problem. I did learn that you can't use a USB Flash drive w/Type C connection to install a Windows ISO. Or at least my MSI motherboard would not see it.