要更换Ubuntu 22的国内源，可以按照以下步骤操作：

1.打开终端，进入 /etc/apt/ 目录

cd /etc/apt/

2.备份原有的 sources.list 文件

sudo cp sources.list sources.list.backup

3.编辑 sources.list 文件

sudo nano sources.list

4.将文件内容替换为以下内容，这是清华大学镜像源的例子，可以根据自己的需要来修改

# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ hirsute main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ hirsute main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ hirsute-updates main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ hirsute-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ hirsute-backports main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ hirsute-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ hirsute-security main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ hirsute-security main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ hirsute-proposed main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ hirsute-proposed main restricted universe multiverse

5.保存并退出编辑器，运行以下命令更新软件包列表

sudo apt update

这样，Ubuntu 22 就已经成功更换了国内源。