硬件：Raspberry Pi 4B
系统：Ubuntu 19.10 (Eoan Ermine) for IOT
官网：https://ubuntu.com/download/iot/raspberry-pi
配置步骤
1. 下载系统镜像
http://cdimage.ubuntu.com/releases/19.10/release/ubuntu-19.10-preinstalled-server-arm64+raspi3.img.xz
2. 烧录至SD卡进行系统安装
3. 系统登陆
默认账号：ubuntu
默认密码：ubuntu
4. 更换镜像源
4.1 备份 apt 源文件
sudo cp -p /etc/apt/sources.list /etc/apt/sources.list.bak
4.2 编辑 apt 源文件，更新为国内镜像源
注意：路径节点不是 ubuntu，而是 ubuntu-ports
注意：系统版本号为 Ubuntu 19.10，对应代号为 eoan
注意：系统版本号为 Ubuntu 20.04，对应代号为 focal
sudo nano /etc/apt/sources.list
#阿里云源 deb http://mirrors.aliyun.com/ubuntu-ports eoan main restricted deb http://mirrors.aliyun.com/ubuntu-ports eoan-updates main restricted deb http://mirrors.aliyun.com/ubuntu-ports eoan universe deb http://mirrors.aliyun.com/ubuntu-ports eoan-updates universe deb http://mirrors.aliyun.com/ubuntu-ports eoan multiverse deb http://mirrors.aliyun.com/ubuntu-ports eoan-updates multiverse deb http://mirrors.aliyun.com/ubuntu-ports eoan-backports main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu-ports eoan-security main restricted deb http://mirrors.aliyun.com/ubuntu-ports eoan-security universe deb http://mirrors.aliyun.com/ubuntu-ports eoan-security multiverse
5. 安装桌面环境（可选择：xubuntu-desktop、lubuntu-desktop、kubuntu-desktop）
sudo apt-get install xubuntu-desktop
6. 重启系统
sudo reboot
异常情况
如果 #5 apt-get 安装出错如下，可以恢复为 ubuntu 官方源进行安装。
Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies:
参考资料
https://ubuntu.com/download/iot
https://opsx.alibaba.com/mirror
https://mirrors.ustc.edu.cn/