How can I install playerctl?

If you just want playerctl, I would suggest you download the .deb-files and install them rather than compiling yourself:

  • libplayerctl (dependency of playerctl)
  • playerctl

Here's what I did on Ubuntu 18.04.1 LTS:

wget http://ftp.nl.debian.org/debian/pool/main/p/playerctl/libplayerctl2_2.0.1-1_amd64.deb
wget http://ftp.nl.debian.org/debian/pool/main/p/playerctl/playerctl_2.0.1-1_amd64.deb
sudo dpkg -i libplayerctl2_2.0.1-1_amd64.deb playerctl_2.0.1-1_amd64.deb

For this to work all other dependencies must be met, of course. They were in my case.