Wavefunctions calculated using HSE06+SOC were used as input orbitals for the G 0 W 0 (+BSE) calculations. While only having a modest effect on the band gap energies, SOC was found to have a relatively significant effect on the spectral shape above the absorption onset, as shown in Section S4. Convergence with respect to the number of virtual states / empty bands, imaginary frequency and time grid points, and electron-hole excitation pairs was confirmed in each case. Given the lack of symmetry reduction, requirement for large numbers of virtual states / empty bands (particularly when including spin-orbit coupling effects)