How to troubleshoot Toshiba 32LF221U19 with black screen, sound works

Setup:

• Toshiba 32LF221U19 (2019 purchase).
• Recently updated software due to manufacturer recommendation (about 1 month prior to issue)
• No HDMI inputs, no other connections
• Plugged directly into the wall

Symptoms:

• TV was working fine and suddenly lost picture. The sound was OK. Wasn’t dropped/electrical surge/damaged in any way
• Using the power switch or the remote, the TV will power on. Red LED indicator will turn on, stay solid, or occasionally slowly dim/flash
• The screen is completely black at all times. The “black” screen is slightly light, meaning that I think the backlight is working. You can tell the difference between the screen being “on” and “off” but no display comes up ever (not even at startup).
• TV fails the “flashlight” test - eg when holding a flashlight to the screen at an angle while the TV is powered on, I can’t see any picture at all
• The sound works, and when you try to navigate the menu with the remote, you can hear it clicking through the options.

Attempted solutions:

• Power cycle using the “unplug for 60 seconds” method (no change)
• Hard reset using the “unplug and hold the power button in while plugging in” option (no change)
• Reset using the “hold power button for 30 seconds” option. (no change)
• Attempted to plug in multiple outlets to make sure the outlet wasn’t bad. tested outlet with a multimeter. No change

How can I troubleshoot this further? I have seen some videos online that show teardown steps to isolate boards and capacitors with a multimeter, but none of them describe my problem exactly. Not sure where to go from here. It was a pretty OK TV while it worked.