Simple answer: the entire $40,000 carries forward to 2020, if you had no income in 2019.
You do not have to use up $3000 each year. Technically you should calculate how much woulda been used if you had prepared a tax return. But for somebody with 0 income, that amount is 0.
The link referenced above refers to pre 2018 tax law (despite the 2019 date on the post). There at no longer personal exemptions. The simple now rule is: If your standard (or itemized) deduction is greater than AGI, without capital loss, then all the capital loss is carries forward.
This confirms what JohnB5677 said earlier (he just referred to the wrong years): "If you had filed a 2019 tax return, and had zero income after deductions other than the Capital Loss Carryover, you will be able to carry the full $40,000 to 2020".
