Ubuntu20.04更换阿里云源后安装软件都会报错：The following packages have unmet dependencies
查看资料，大概是ubuntu本身的源比较版本较老，而阿里云的源比较新，因此版本不匹配造成依赖的库不匹配，所以只要将阿里云的源换回Ubuntu官方源
替换源
Ubuntu20.04LTS的清华大学源如下：
# 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/ focal main restricted universe multiverse# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiversedeb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiverse# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiversedeb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiverse# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiversedeb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted universe multiverse# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted universe multiverse# 预发布软件源，不建议启用# deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-proposed main restricted universe multiverseUbuntu 的软件源配置文件是 /etc/apt/sources.list，在配置之前最好做个备份，然后将以上内容复制到该文件进行替换。
更新源
更新本地软件源列表：sudo apt-get update
根据刚才更新的软件源更新本地软件库：sudo apt-get upgrade
然后可以正常安装了。
其它
如果以上执行完还是不行，可以参考此链接里面回答的几种方法：What is the step-by-step procedure to fix the “The following packages have unmet dependencies”?