I have used Ubuntu 14.04 LTS and 15.10 and have had no problems installing anything via the Software Centre. However, upon changing the software center in 16.04, I am having trouble finding many things in the new 'Ubuntu Software' app; let me explain this a bit further.
In the previous versions, I could query ubuntu-restricted-extras and see the package and install it - such query yields no results in 16.04 but the
sudo apt-get install ubuntu-restricted-extras command allows me to install it.
Furthermore, other things such as Steam for playing games, google chrome, and playonlinux are no longer in the Ubuntu Software app and I am having to install them from their respective websites, most of them install fine but playonlinux is now really buggy and I never had that problem when installing from the old Software Centre.
TL;DR - Why is the new Ubuntu Software app lacking many of the applications that were in the older Ubuntu Software Centre? Is it possible to make these appear in the new app that 16.04 uses (and will they work properly if so)?