dht@dht-PC:~/Desktop$ sudo apt-get update
请输入密码:
验证成功
E: 软件源列表 /etc/apt/sources.list 第 2 行中的类别 “set” 无法识别
E: 无法读取源列表。

sources.list 内容如下

dht@dht-PC:~/Desktop$ cat /etc/apt/sources.list.
sources.list.bak.20230218  sources.list.d/        
dht@dht-PC:~/Desktop$ cat /etc/apt/sources.list.bak.20230218 
#! /bin/sh
set -e

which update-grub >/dev/null 2>&1 || exit 0

if type systemd-detect-virt >/dev/null 2>&1 &&
   systemd-detect-virt --quiet --container; then
        exit 0
fi

set -- $DEB_MAINT_PARAMS
mode="${1#\'}"
mode="${mode%\'}"
case $0:$mode in
    # Only run on postinst configure and postrm remove, to avoid wasting
    # time by calling update-grub multiple times on upgrade and removal.
    # Also run if we have no DEB_MAINT_PARAMS, in order to work with old
    # kernel packages.
    */postinst.d/*:|*/postinst.d/*:configure|*/postrm.d/*:|*/postrm.d/*:remove)
        if [ -e /boot/grub/grub.cfg ]; then
                exec update-grub
        fi
        ;;
esac

exit 0
dht@dht-PC:~/Desktop$ 

参考了 https://www.shuzhiduo.com/A/8Bz8r64X5x/

替换为 ustc 中科大镜像源

中科大镜像源

## Generated by deepin-installer
deb [by-hash=force] http://mirrors.ustc.edu.cn/deepin panda main contrib non-free
#deb-src http://mirrors.ustc.edu.cn/deepin panda main contrib non-free