Ubuntu 安装 docker-ce 提示 Package docker-ce is not available, but is referred to by another package.

Open /etc/apt/sources.list.d/docker.list and add the following content

deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable

Update and install

sudo apt-get update

If the process of sudo apt-get update is slow, you can try to use the domestic mirror

sudo apt-get install docker-ce