sudo nano /etc/apt/sources.list然后把里面的内容全部删除，替换为下面 一整段
# 清华大学 TUNA Ubuntu Ports 镜像源 (适用于 Jetson, Ubuntu 20.04)
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ focal main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ focal-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ focal-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ focal-security main restricted universe multiverse保存后退出（Ctrl+O → 回车 → Ctrl+X）。
然后执行以下命令刷新缓存并修复包依赖：
sudo apt clean
sudo apt update --fix-missing
sudo apt --fix-broken install -y
sudo apt update