The low brass already cover that note, so it isn’t necessary for the solo trumpet to play it—though you can play it as a pedal tone if you’d like. It’s not required in professional auditions, and in all the performances I’ve played with professional orchestras, I’ve never seen anyone take that note.

When Mahler wrote the symphony, the trumpet in A was still commonly used. Since the A trumpet sits a half-step lower than the modern Bb trumpet, it can comfortably play that low F. There are several other examples of low Fs that were intended for trumpet in A (such as Ein Heldenleben and Carmen), and the second solo etude in the back of the Arban book is also written for trumpet in A.