China has urged local companies to avoid using Nvidia Corp.’s H20 processors, particularly for government-related purposes, complicating the chipmaker’s attempts to recoup billions in lost China revenue as well as the Trump administration’s unprecedented push to turn those sales into a US government windfall.Over the past few weeks, Chinese authorities have sent notices to a range of firms discouraging use of the less-advanced semiconductors, people familiar with the matter said, asking not to b...