升级到 Ubuntu-20.04 后，我无法安装 pgadmin4。此外，任何其他版本的 pgadmin 都不起作用。
它显示以下错误：
Package pgadmin4 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'pgadmin4' has no installation candidate
E: Unable to locate package pgadmin4-apache2
在我的“pgdg.list”文件中，可以从下面的命令访问
sudo nano /etc/apt/sources.list.d/pgdg.list
我有：
deb http://apt.postgresql.org/pub/repos/apt/ focal-pgdg main