Is it possible to manage (pair) Logitech Unifying devices in Ubuntu 15.10?
According to the this answer to the original question about solaar, there is no longer a need for a ppa as solaar is now included in the Ubuntu "universe" repositories.
If you already have the "universe" enabled then you can install it via the Software Center by searching by it for name.
If you do no have it enabled there are a couple of ways to do that.
Use the Software Center to search for
solaar. It should find it but tell you that is is avialble tru the "universe" repos and where the install button should be will be a button to "Use Source" click this and the rest should happen automatically.If searching in the Software Center does not work, or you wish to do it yourself, you can do this with
Software and Updates. Search for it using the dash, click on it and you will get window like this
The second box down needs to be checked to allow universe sources. Check the box, enter your password in the box that pops up. This will enable the source. When you close the Software and Updates window, it will ask you if you want to reload you software sources.
Answer Yes and your software sources will update, you will then be able to find and install solaar in the software center.
Note: If you want the indicator and better integration with Unity(or Gnome shell), look in the "optional add ons" section on the More info" page of the software Center. You will want to click on(or make sure it is already selected) the "solaar gmone3" addon or you will only have the terminal version of solaar.
You can also install via the terminal by sudo apt-get install solaar-gnome3
This will install the packages needed to integrate with Unity and Gnome DE and will pull in and install solaar as well.
If you only want the command line of solaar, you can get that by sudo apt-get install solaar.