1. Install PulseAudio Volum Control (pavucontrol): a graphical sound management tool developed based on GTK.
open terminal
Enter the command: sudo apt install pavucontrol
Then, wait for the installation to finish.
2. Continue typing the command: pavucontrol
A graphical interface will appear, move the small arrow on the menu bar to find the Configuration menu bar.
Find the Built-in-Audio option and select Analog Stereo Output. The rest of the options are off.
3. Find the Output Devices menu bar and select Headphones.
4. Then find a video to test the following. If you can, close the GUI. Finish.
5. There is another situation, such as firefox, etc., the browser itself disables the sound, you can confirm it, but there are not many cases.