The reason that negative power prices look like they would be good for consumers is that it seems like they should lower their monthly bills. But in practice their bill should stay the same, even if there were significant periods during which energy prices were negative. Why? The negative prices don't indicate that the cost of power production is negative for the power company, so the power company is losing money. The power company has to recoup those losses somehow, and they do it by charging more when power prices are positive.
In order to take advantage of negative power prices, a power consumer would have to dynamically increase their power consumption in response to the negative prices. If they have any significant power storage capacity, maybe they could store power and sell it back to the grid when prices go positive, or maybe turn on their mining rig while prices are negative, if they go negative frequently.