Unable to boot zorin os 16 core after iMac install

Hello I am new to Linux an I am trying to install zorin os in an iMac of 2010.

I installed the os using safe drivers and in the process I chose to delete everything on the hard drive and install third party drivers.

But as the title says, when I boot to zorin the only thing appearing in the screen is a (-) just that nothing else and after about 10 seconds it disappears so after researching and even trying the method from the website where you press ESC nothing happened.

I think that it's either a graphic problem or an iMac problem. Please help me using Mac OS X is a pain in the a** cause I am not able to download anything.

Hi, and welcome!
Did you use Balena Etcher to install?

Yes. However I did some research and discovered that my model iMac 21.5 mid 2010 has a graphical problem, you see it has an old Radeon GPU.
Now the problem is how will I be able to fix that.
Some use an external monitor but I want to use the regular monitor after the driver fix and I don't know if it will work or the how to do it.

Hi, Take a look at this askubuntu thread in its entirety. Hope something will work!