How can I download the OS X 10.7 Lion Installer

Mac OS X Lion is only available as a $20 from the Apple Online Store (not the App Store) when you purchase

you will e-mailed a redeem code which you use in the App Store (not the Apple Online Store).

From macOS Sierra Apple stopped the Purchased section of the App Store showing previously downloaded

OS's.

If you want to try internet recovery follow this,

The certificates for several of Apples OS's expired in October 2019, Apple have been very poor at getting these updated on their Recovery Servers with valid certificates. This may be the problem you are experiencing. 

Try this workaround, we are going to set the time and date on your mac to a date previous to the expiry date of the certificates.

Connect your mac to your router via cable, not WiFi

Boot to your Recovery HD, click on Utilities in the menubar select Terminal.

Make sure WiFi is switched off, it can reset the date back to today.

Enter a new date, for example or just copy and paste

sudo date -u 011421002014

press Return

enter your password

press Return

If Terminal returns an error saying sudo : command not found, then try again without sudo.

Now try downloading the OS.

If this works then when the OS is installed and booted up you can Open System Preferences> Date & Time

and reset the time back to today.

Your 2019 iMac can install Yosemite or El Capitan which are available as free downloads.

If you want more information about that then ask.

There could be dozens of reasons why it may not work. You will only find out when you try.

Yes El Capitan can be installed on that iMac, you used a USB you already had, but if this had been

created before October 2019, it would fail because the certificate for it has expired, that is mentioned

earlier in my first post.

You can download El Capitan with the new certificate from here,

(you do not need to reset the date and time for this method)

How to upgrade to OS X El Capitan – Apple Support

Go to Section 4 and click on Download OS X El Capitan.

This downloads InstallMacOSX.dmg to your Downloads folder.

The next section can only be done on a mac that is capable of running El Capitan,

a mac that came preinstalled with an OS later than El Capitan will refuse to do the next bit.

When downloaded open to InstallMacOSX.pkg, double-click on

that and an installation window will open, this does not install El Capitan

but converts the InstallMacOSX.pkg to the Install OS X El Capitan.app which 

you will find in your Applications folder, it should be 6.2GBs in size.

 (If the installation window asks which disk you want to install to, you must pick 

the disk that you are booted to at the time. Not any internal or external disk that 

you want to eventually install El Capitan on, that is for later.)

Now you are ready to create a bootable USB installer disk using the Install OS X El Capitan.app

in the Applications folder and the createinstallmedia command in the Terminal app. 

Read the instructions here,

How to create a bootable installer for macOS – Apple Support

Get a very long Ethernet cable or move the mac closer to her router, as said before WiFi has a habit of

changing the date back to today.

If you manage to redeem the Lion installer then you will need to create a bootable USB so you can transfer it

to your friends iMac. In order to do that you may have to seek out a copy of the old Lion DiskMaker or DiskMaker 3,

https://diskmakerx.com/download/ and hope it still works. You do not need to reset the date and time using this method.