Periodograms of HD 67458 (left) and HD 88595 (right). From top to bottom: Lomb-Scargle periodograms of CHEOPS, ESPRESSO and TESS observations computed on the whole dataset are shown in black. Their respective averaged periodograms, resulting from the average of the periodograms of each CHEOPS visits, ESPRESSO nights, or TESS 8-h subseries, are shown in red. Yellow lines represent the best-fitting Harvey models, given in Eq. (1), that fits the Lomb-Scargle periodograms of each datasets. The different components of this model (white noise, oscillation modes, granulation, supergranulation) are represented in dotted yellow. When relevant, the different cut-off frequencies are represented by vertical lines: ν_cut in green (used to infer the level of white noise), ν_max in blue (frequency only relevant for ESPRESSO data of HD 88595), f_H in cyan (frequency generally close to ν_cut), and f_g in magenta.