How Do I Transfer Mac Ownership?

I am transferring an iMac running High Sierra to a new owner, a family member. I do not want to delete everything, as apart from emails and email accounts and some personal files I will delete I am happy to leave the apps and files remaining.
I don’t want to have to present a fresh drive to the new owner but I know the Apple ID assigned to the computer will have to be different with no reference to mine remaining. Can it be done and if so how?
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Des