It hit the U.S. eShop and Steam on May 2nd. There is also a limited number of physical copies to be released sometime later this year. From the eShop page:

"Where courage and conviction dictate, pull the trigger of your heart!"

"Trigger Heart Exelica", a shooting game with a famous family of mecha families released in the arcades in 2006, has finally been reissued on Nintendo Switch™! In addition to Arcade Mode and Story Mode, Arrange Mode and Training Mode have been added. In addition to Arcade Mode and Story Mode, Arrange Mode and Training Mode have been added, as well as Vertical Screen Mode and Internet Ranking Mode. A sound mode with additional arrangement sources will also be included. This is the culmination of all the hard work that shooting game fans have put into this title.