Generalised Lomb-Scargle periodogram of the complete HARPS RV data set and different activity indexes derived with SERVAL. The horizontal dashed lines mark the FAP level at 0.1%. The vertical yellow band marks the rotation frequency of TOI-776 at 0.0473 day⁻¹ (P_rot ≈ 21.1 days) and its 3σ uncertainty. The vertical dashed red and blue lines mark the orbital frequencies of TOI-776 b and c, respectively.