阿里云源
https://developer.aliyun.com/mirror/ubuntu-ports?spm=a2c6h.13651104.d-1008.3.71414763blCksm
deb https://mirrors.aliyun.com/ubuntu-ports/ focal main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu-ports/ focal main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu-ports/ focal-security main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu-ports/ focal-security main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu-ports/ focal-updates main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu-ports/ focal-updates main restricted universe multiverse
# deb https://mirrors.aliyun.com/ubuntu-ports/ focal-proposed main restricted universe multiverse
# deb-src https://mirrors.aliyun.com/ubuntu-ports/ focal-proposed main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu-ports/ focal-backports main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu-ports/ focal-backports main restricted universe multiverse
更新华为源也行
https://zhuanlan.zhihu.com/p/616665905
deb https://repo.huaweicloud.com/ubuntu-ports/ focal main restricted universe multiverse
deb-src https://repo.huaweicloud.com/ubuntu-ports/ focal main restricted universe multiverse
deb https://repo.huaweicloud.com/ubuntu-ports/ focal-security main restricted universe multiverse
deb-src https://repo.huaweicloud.com/ubuntu-ports/ focal-security main restricted universe multiverse
deb https://repo.huaweicloud.com/ubuntu-ports/ focal-updates main restricted universe multiverse
deb-src https://repo.huaweicloud.com/ubuntu-ports/ focal-updates main restricted universe multiverse
deb https://repo.huaweicloud.com/ubuntu-ports/ focal-backports main restricted universe multiverse
deb-src https://repo.huaweicloud.com/ubuntu-ports/ focal-backports main restricted universe multiverse
## Not recommended
# deb https://repo.huaweicloud.com/ubuntu-ports/ focal-proposed main restricted universe multiverse
# deb-src https://repo.huaweicloud.com/ubuntu-ports/ focal-proposed main restricted universe multiverse