My work PC never connects to the internet. For security it uses the "3 feet of air" firewall.
Can the "stuff" be downloaded from the site on this PC and then copied to the work PC?
or is there an offline version of the IDE?
or will the previous version 1 install and run offline?
Sorry, for "or is there an offline version of the IDE?" I mean is there an offline version of the installer that includes the "stuff".
Both IDEs work off-line.
However IDE 2.x does not come with the AVR board package and that's one of the things that the IDE wants to install; else you can't use it. After that you can use it off-line.
IDE 1.x comes with an older version of the AVR board package (that's not a problem) and is therefore ready to use when it's installed.
So installing IDE 1.8.19 will solve your off-line problem. Be aware that you in that case only can compile for AVR based boards like Uno and Mega and not for other boards.
If you have another PC (with internet access) there are other options as far as I know. You can install IDE 2.x on there, do what is needed and next copy a directory over to your work PC.
Note
If you need Arduino for your work, the IT department should allow access for the IDE.
Your question has been given its own topic.
Hi @olly.
As @sterretje said, yes you can do that. If you would like instructions, please add a reply here on the forum thread to tell us which operating system (e.g., "Windows") you are using on the online PC and on the work PC.
Thanks for your detailed reply that describes the complete situation and solutions.
That is an excellent work around.
I am using Windows 10.
Install IDE 2.x on a Windows PC with internet access.
Start it up; it will download the additional "things" like the board package.
Install any additional board packages that you need (e.g. ESP32).
All necessary stuff will be found in the directory C:\Users\yourUsername\AppData\Local\Arduino15 so copy that directory to an external storage (USB drive, memory stick).
Connect the external storage to your PC without internet. Copy the directory from the external storage to the same path where it came from.
If I missed something, ptillisch will correct me.
You posted this in the topic that you originally hijacked 
Moved it for you.
Excellent!!
It now runs and the libraries are visible.
Sorry about the hijacking, I didn't realize I did it.
It's easy to get confused hanging upside down from the bottom of the planet.
If you're referring to the files in Arduino15, they are not libraries but board packages (although they do contain some standard libraries like Wire).
It's better to start your own topic. Although symptoms might be the same the root cause might be different.
Thanks for the advice.