  The dynamical structure factor is an important observable of quantum magnets
but due to numerical and theoretical limitations, it remains a challenge to
make predictions for Hubbard-like models beyond one dimension. In this work, we
study the magnetic excitations of the triangular lattice Hubbard model
including next-nearest neighbor hopping. Starting from the 120$^{\circ}$ and
stripe magnetic orders we compute the magnon spectra within a self-consistent
random phase approximation. In the stripe phase, we generically find accidental
zero modes related to a classical degeneracy known from the corresponding
$J_1$-$J_2$ Heisenberg model. We extend the order-by-disorder mechanism to
Hubbard systems and show how quantum fluctuations stabilize the stripe order.
In addition, the frustration-induced condensation of magnon modes allows us to
map out the entire phase diagram which is in remarkable agreement with recent
numerical works. We discuss connections to experiments on triangular lattice
compounds and the relation of our results to the proposed chiral spin liquid
phase.
