MacBook Air A1932 (2019) display remains black after closing and opening

What you have provided makes me think that the culprit is the flex cable used between the Mac's logic board and its display panel. These do then to wear out over time, and when then do, can exhibit these types of symptoms.

With your Mac model, the display signal and lid-angle detection both pass through the flex cable assembly and the embedded hall sensor in the lid. A failing display flex, weak backlight power line, or a misbehaving hall sensor can result in the Mac thinking the display is still closed even when it’s open. That leads to exactly what you’re seeing: system wakes, keyboard lights respond, but the panel stays black with no backlight.

Here’s are some suggested troubleshooting steps you can try before considering contacting Apple Support directly for a potential repair:

• Start by testing with an external display connected to your Mac. If the Mac reliably wakes and shows video externally after a lid-close/open cycle, the logic board GPU output is fine and the issue is contained to the display assembly or flex cabling.
• Next we can check the lid-sensor by using Apple’s built-in `pmset -g log` to confirm whether the Mac registers an “Open” event when the lid is lifted. If the hall sensor is stuck or intermittent, the display won’t wake. To do so, open the Terminal app, and then, enter the following command: pmset -g log | grep -i lid This filters the power-management log to only show entries related to lid open/close events. What you are looking for are entries, like: "Lid Opened" or "Wake from Sleep due to Lid Open" or "Entering Sleep due to Lid Close". If the sensor is working correctly, you'll see an entry every time the lid is lifted or closed.
• Finally, you want to verify if the display panel's backlight only failed. To do so, shine a bright flashlight at an angle on the screen after waking. If you faintly see the desktop, the backlight line is failing.

These are the only steps you can do without opening up the Mac. If you need to go to this step you should consider letting Apple check the Mac's display flex cable, logic board, and display panel. They should be able to perform these steps for free. Should they find any issues, they will provide you with an estimate before they proceed with any repairs.

Great! Please post back your results.