Six hours of work? Lie the other 2 and call it a day.
Or, renegotiate a contract for 6 hours per day.
Given how much productivity I presume you bring, I’d lie.
I don’t feel bad about it since companies care too little (in general). If they care, then I would care. E.g. a 10x more productive engineer doesn’t get 10x the pay. I met one of these people, they lied. They worked 2 hours, shipped one hour of code in production, saved the other one to commit on a rainy day and still got employee of the year because they were by far the most productive.
You could also become a freelancer, then you don’t have to lie.
My point is: six hours of productive work should be enough.