I followed the steps to sign out of iCloud but my photos are still accessible on the Mac I am giving away. What do I do?

Follow ALL of the steps in the "Related Article." What to do before you sell, give away, or trade in your Mac - Apple Support.

As per this article https://support.apple.com/en-in/guide/mac-help/mh36825/10.14/mac/10.14

You’re also asked whether you want to download or remove photos and videos that aren’t fully downloaded from iCloud Photos to your Mac. After you sign out of iCloud in iCloud preferences, downloaded Photos and videos aren’t kept up to date with changes on your other devices. If you have photos in My Photo Stream that aren’t imported to your Mac, they no longer appear on your Mac.

So set up photo library https://support.apple.com/en-in/HT204264 and it preferences https://support.apple.com/en-in/guide/photos/pht5156cc968/4.0/mac/10.14

And download the https://support.apple.com/en-in/HT209454

The photos can be deleted and erased permanently https://support.apple.com/en-in/guide/photos/pht3bfab2f96/mac from system photo library https://support.apple.com/en-in/guide/photos/pht211de786/4.0/mac/10.14 of Mac

These photos will be erased from iCloud.com and Mac ( you must not click on keep a copy of photos ) when following this article What to do before you sell, give away, or trade in your Mac - Apple Support.

I cannot clean my Mac that I am returning to the factory. What about the stuff on the computer that I cannot remove?