解决方案:
安装并打开pavucontrol:
sudo apt install pavucontrol
pavucontrol
按照下面两幅图画红圈的设置去做,然后把音量打开,就可以在耳机里面听到声音啦
参考:
https://blog.youkuaiyun.com/weixin_36340947/article/details/78604865
https://blog.youkuaiyun.com/wangjinbao5566/article/details/52689889