Dana White has been adamant that, coronapanic or no, the UFC would continue to hold events so long as the US government was in operation. True to his word, now he says UFC 249 will go ahead on April 18th as planned, there just won't be any live audience.
He won't yet say where it will be held but considering the economics of this I'm guessing he will be looking to minimize the hit from not having a live gate (big fights usually gross over $10 million in gate alone) so he's probably not going to want to pay the rent on any of the usual venues. Provided their infrastructure will support it I'm thinking he'll use the production facility where they film the fights in his TV series, The Ultimate Fighter. But I don't know squat about producing a TV show, or how those requirements change from the TV show to a major production like a championship fight.
But won't it be odd to watch a full-blown UFC without the fighter's entry pomp and the crowd noise. So you'll hear the impact of every blow landed. The PPV might actually be a better viewing experience. It'll be interesting to see how if affects the fighters, too, not being able to feed off the crowd noise.