There are now rapid antigen tests available in the US that test for influenza A, influenza B, and COVID-19. (In some other countries, there are 6- or 9-pathogen rapid antigen tests available which include additional pathogens like RSV, adenovirus, parainfluenza, etc..)
Having some tests around and using them when getting a feverish illness with respiratory symptoms can help determine what it is (or is not).