If you have never added a PPA on your system before, you might need to run this command first:
sudo apt install -y software-properties-common
Add the PPA of Monitor and then install it:
sudo add-apt-repository ppa:stsdc/monitor
sudo apt install com.github.stsdc.monitor
Monitor will be available from the Applications menu.
Check dependencies in the deb control file.
Clone:
git clone --recursive https://github.com/stsdc/monitor
cd monitor
To build with the wingpanel indicator:
meson builddir --prefix=/usr -Dindicator-wingpanel=enabled
Alternatively, to build without the wingpanel indicator:
meson builddir --prefix=/usr
Install:
cd builddir
sudo ninja install
G_MESSAGES_DEBUG=all GTK_DEBUG=interactive io.elementary.monitor