Ubuntu 18.04 removed the gksu package entirely from its repositories.
The rational behind this is that gksu is thought to be used only in this way:
gksu gedit /some/root/setting
But there are other usages of gksu as well. Gksu is an important program because unlike sudo or graphical programs like pkexec it prevents other programs from stealing focus.
So when you want to type your password using simple cli sudo, and some chat window pops up, what happens is that the password is entered into the chat window (if you don't look at the screen for a moment), and your root password is sent to you chatting buddy. It happened to me once and I don't want it to happen ever again.
This is why gksu is ideal security wise, and I use it often at command line level. So not to launch gedit, but to do command line stuff, e.g. apt-get update && apt-get upgrade or execute some bash scripts.
And no, pkexec is not an alternative to gksu, because 1) it does not execute scripts, only binaries and 2) it doesn't prevent other programs from stealing focus.
Secondly, you can also use gksu to ask for non-root passwords in a secure manner. For example:
ccrypt -K `gksu -p --message "Password:"` -d data.tar
So my question is: what program can be used as an alternative to gksu in these cases?