How to install older gcc package using APT from a repository?

I have GCC v9. But I'm trying to install a GCC 4.8.1 version to test a library compilation on that very old version of GCC.

The version is not available in the official Ubuntu repos,it is deprecated, but I've found it in other mirrors as told by the official GCC website. This one seems like popular one:

I have very little knowledge of linux package systems except for the basic. I want to keep both versions. So I should do this:

sudo apt -y install gcc-4.8.1 gcc-9

The reason why I want to use this command and not install it from the file, apart from the difficulty of doing that for me, is that I'm following a guide in order to have several GCCs on my system:

When I add the url to the sources.list file seems like it is working.

sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt update -q

But when I try to call the install with gcc-4.8.1 or gcc-4.8 , or even gcc-4 the package doesn't exist.

Package gcc-4.8 is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source E: Package 'gcc-4.8' has no installation candidate

Also, I don't know if websites like these can be added to the repos list in order to find the package using APT:

[EDIT]

I downloaded the package from the website I linked. I have no idea how to install this by hand. If only I could find a repository that could help me with this... I have no idea how to make APT help me with the installation.

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