Given your points on hardware, I think MX Linux might be a better option than Ubuntu as you say. Linux is different than Windows both in UI and in user experience but it is also more intuitive I think. The good thing is that a "live USB", the way Linux is installed these days mostly, allows you to test and look around without installing it and they are not hard to make, it requires a program and downloading the OS.
From Ubuntu's site they recommend balenaEtcher as the program to copy/burn the OS since it supports multiple platforms, and looking at their site they do have a "legacy" version for older hardware. You might provide a better option regarding something to burn an image that runs on Windows 7 though, as their site says they have a version that is compatible but is not clear if the one labeled as "legacy" is the one they are referring to.
If I may, I think you complicated instructions a little bit above.
There are only three steps: 1) Downloading OS image (the name for a file that needs to be burned into a media in order to run) 2) Burning it into the selected media, which has to be at least 2GB, for Ubuntu at least. and 3) Turning off the computer and and booting up again with the media inside or plugged in to the computer. Most modern Linux distros already boot if plugged in, so no need to tell the computer to change it's boot loader.
Re: Ubuntu
A quick search showed that Intel Core Duo is 64 bits from the blog linked below
"Intel Core 2 is a 64 bit CPU that dates back to 2006.
MX linux would be my first choice although you could try running debian 11."
and some other points regarding it
https://www.linuxquestions.org/questions/debian-26/best-debian-linux-version-for-a-core-2-duo-laptop-4175711538/#:~:text=Intel%20Core%202%20is%20a,could%20try%20running%20debian%2011.&text=Probably%20best%20to%20avoid%20Gnome%20or%20KDE%20though.&text=I%20also%20recommend%20Debian%2011.
Given your points on hardware, I think MX Linux might be a better option than Ubuntu as you say. Linux is different than Windows both in UI and in user experience but it is also more intuitive I think. The good thing is that a "live USB", the way Linux is installed these days mostly, allows you to test and look around without installing it and they are not hard to make, it requires a program and downloading the OS.
From Ubuntu's site they recommend balenaEtcher as the program to copy/burn the OS since it supports multiple platforms, and looking at their site they do have a "legacy" version for older hardware. You might provide a better option regarding something to burn an image that runs on Windows 7 though, as their site says they have a version that is compatible but is not clear if the one labeled as "legacy" is the one they are referring to.
If I may, I think you complicated instructions a little bit above.
There are only three steps: 1) Downloading OS image (the name for a file that needs to be burned into a media in order to run) 2) Burning it into the selected media, which has to be at least 2GB, for Ubuntu at least. and 3) Turning off the computer and and booting up again with the media inside or plugged in to the computer. Most modern Linux distros already boot if plugged in, so no need to tell the computer to change it's boot loader.