Light curves for four of the targets with epoch photometry. Top left: AG Car, an LBV properly classified in R23. Top right: ALS 12 688, not given a classification type there but classified as an eclipsing binary in paper II of this series (Holgado et al., in prep.). Bottom left: HD 3885, classified as a slowly pulsating B star in R23 and as an α² CVn variable in SIMBAD. Bottom right: OGLE LMC-CEP-101, classified as a Cepheid in that paper. The last three panels are phased with the best fitting period in each case (2.020 11 d, 1.815 67 d, and 8.190 73 d, respectively). The solid circles with error bars indicate the Gaia DR3 epoch measurements while the open circles with double error bars indicate the average magnitudes and the total and astrophysical dispersions determined in this paper (when both are similar the double error bars overlap). For OGLE LMC-CEP-101 the median magnitudes are subtracted in the vertical axis to allow for a higher dynamical range to be visualized.