S/N_PSD of observed TESS light curves as a function of the TESS magnitude. The black horizontal line indicates the limiting S/N_PSD for a reliable orbital period detection, S/N_PSD = 0.004, determined with simulations (see Sect. 6.1). In Sect. 4.6.2, periods were provided for 2XMM J154305.5-52270, GQ Mus, and J1424-0227 (marked here with different plotting symbols and colours), but our new periods as well as previous values presented for them in the literature remain questionable, consistent with the location of these systems beyond the S/N_PSD threshold.