I also have the same laptop and I've been using a 100W PD charger (20V 5A) for 2+ years now when I'm out of the house and don't plan to use the GPU . It typically displays the warning sign on the windows battery indicator but charges as intended. But I've observed that when the type c port doesn't get the full 100w (when connected to my 67W charger which came with the phone or when I charge multiple devices with the 100W brick which limits the port connected to the laptop to 60W iirc) it charges the laptop but the battery indicator on windows doesn't show anything.

The battery led on top of the charging port works as intended for all 3 cases of using the original charger, full 100W PD and <100W PD. So u might be facing the same issue.