The official personal package archive on launchpad contains daily builds of the main Inkscape development branch (master) for Ubuntu, starting from Ubuntu 18.10 (and Ubuntu derivatives, e.g. Linux Mint, elementary OS).

To add the ppa to your list of software sources, open a terminal and type:

$ sudo add-apt-repository universe
$ sudo add-apt-repository ppa:inkscape.dev/trunk

Agree to the questions it asks.

Then refresh the list of available packages with:

$ sudo apt-get update

Then get the latest Inkscape development version with:

$ sudo apt-get install inkscape-trunk

This will replace your stable Inkscape version from the Ubuntu repositories.

To go back to the version that is officially available in Ubuntu, remove the ppa from your package sources or disable it, uninstall Inkscape, update the package cache, then install the stable version.

$ sudo add-apt-repository --remove ppa:inkscape.dev/trunk

If you're afraid of messing up your main Inkscape installation, you can also use Ubuntu inside a virtual machine such as VirtualBox or VMware, or the available AppImage packages, or follow the instructions from https://gitlab.com/Moini/make_ink .