How to keep laptop speakers working when the lid is closed while using an external monitor via HDMI?

I'm running Arch Linux on my laptop and have an external monitor connected via HDMI. I want to close the laptop lid while using the external monitor, but I want the laptop's internal speakers to keep working because I don’t have external speakers on the monitor. I’ve already configured my power management settings to prevent the system from suspending when the lid is closed. Specifically, I’ve edited the /etc/systemd/logind.conf file with the following settings:

HandleLidSwitch=ignore
HandleLidSwitchExternalPower=ignore

However, even after this, the laptop’s internal screen still turns off when I close the lid, which is not what I want. I’d like to only turn off the internal screen while keeping the speakers active and the system running as usual. I have also checked the power settings in KDE Plasma and set it to "Do nothing" when the lid is closed, but the issue persists. What am I missing or doing wrong? How can I close the lid and turn off the screen while keeping the internal speakers working when using an external monitor?