As you may know, SMPlayer is a front-end for MPlayer, having support for video, DVD and VCD playback, has some advanced features like support for MPlayer filters and keeps track of the settings of all the played files, resuming a closed movie from the moment it was closed.
The latest version available is SMPlayer 18.10, which has been released a while ago. To see the changes, please consult the changelog.
In order to install SMPlayer on Ubuntu 18.04 Bionic Beaver, Ubuntu 18.10 Cosmic Cuttlefish and other derivative systems, you need to add the PPA to your system, update the local repository index and install the smplayer and smtube packages. Like this:
$ sudo add-apt-repository ppa:rvm/smplayer
$ sudo apt-get update
$ sudo apt-get install smplayer
Optional, to remove smplayer, do:
$ sudo apt-get remove smplayer