iMac 2009 black screen

Hi - I’ve an old iMac that I decided to install Linux on to give it a modern operating system and make it run faster. I tried Mint but eventually tried Zorin OS and I really like it….but, the screen sporadically goes black. You can still hear the sound but the only solution to get the screen back on is to turn it off and on again. Any thoughts on how to rectify the issue?

Welcome!

Which driver are you using? Launch Software & Updates, navigate to the top 'Additional Drivers' tab and see what's installed:

I'm always bleeding edge - but sometimes that doesn't always work out. Since you've got something from '09, try the 470 driver; or the Nouveau driver, the open source one.