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.

If you plan to install WITH a wingpanel-indicator

sudo apt install build-essential cmake sassc valac libgtk-3-dev libgee-0.8-dev libgranite-dev libgtop2-dev libwnck-3-dev libhandy-1-dev libudisks2-dev libjson-glib-dev libflatpak-dev libxnvctrl-dev liblivechart-1-dev libwingpanel-dev

Alternatively, if you plan to install WITHOUT a wingpanel-indicator

sudo apt install build-essential cmake sassc valac libgtk-3-dev libgee-0.8-dev libgranite-dev libgtop2-dev libwnck-3-dev libhandy-1-dev libudisks2-dev libjson-glib-dev libflatpak-dev libxnvctrl-dev liblivechart-1-dev

1. Clone:

   git clone --recursive https://github.com/stsdc/monitor
   cd monitor

2. To build with the wingpanel indicator:

   meson builddir --prefix=/usr -Dindicator-wingpanel=enabled

   Alternatively, to build without the wingpanel indicator:

   meson builddir --prefix=/usr

3. Install:

   cd builddir
   sudo ninja install

G_MESSAGES_DEBUG=all GTK_DEBUG=interactive io.elementary.monitor