Top Panel: Redshift evolution of the global 21 cm signal for different values of $f_{X,\mathrm{esc}}^{\mathrm{PBH}}$ (keeping the escape fraction of X-rays from SF galaxies, $f_{\mathrm{X},\mathrm{esc}}^{\mathrm{SF}}$, fixed at 1.0), as indicated in the plots. The blue and magenta curves correspond to the SF-only and SF plus PBH scenarios, respectively. In the leftmost panel, with $f_{X,\mathrm{esc}}^{\mathrm{PBH}}=1$, the SF-only case exhibits a much deeper absorption trough than the SF and PBH scenario. This difference arises because the additional X-ray emission from PBH-seeded galaxies produces excess heat, increasing the temperature of the IGM (T_k) as shown in the bottom panel of the figure. As $f_{X,\mathrm{esc}}^{\mathrm{PBH}}$ decreases further (moving towards the right), the X-ray output from PBH-seeded galaxies and the corresponding T_k diminish, leading to a progressively smaller difference between the two signals. We also note the difference in the signals around 25 ≳ z ≳ 20. This can be attributed to the fact that SF and PBH together produce significantly more Ly-α photons compared to the SF-only model, as is also evident in panel (b) of 1.