No, you cannot use the Lenovo L15 monitor directly with an HDMI to USB-C adapter if your laptop only has an HDMI output. The L15 monitor requires a USB-C connection to receive both the image and the power supply. An HDMI to USB-C adapter can convert the HDMI signal to a USB-C signal, but it cannot supply power via the HDMI output of your laptop, which is required to operate the monitor.