Since a long time, I was trying to get my SDRPlay running with gqrx on Ubuntu. A while ago, I successfully compiled everything I needed, but this lesson took hours and after the next Ubuntu update, it did not work anymore. Now I found a solution that is much easier. I did a lot of other changes on my system in parallel, so I am not 100% sure that the following steps are enough to get it running, but it works now for me.
Running SDRPlay with gqrx on Ubuntu 18.10