After reading up on different Linux distros (whoa, that's a rabbit-hole!), I installed and tried a few before settling on Ubuntu MATE. I chose it because it has a large community, lots of support, examples etc and will run on a Rasberry Pi. I preferred the MATE desktop over the standard Ubuntu one too. I installed Ubuntu MATE on an old netbook for development purposes, then ended up dual-booting with it on my old main laptop too, then of course set about installing it on the shiny-new RPi3B+ that I recently purchased...

At the time of writing, the RPi3B+ will not run most Linux distros. That's the "B+", the "B" is fine. The architecture of the two are different and the B+ will only run Raspbian out of the box, a fact that isn't immediately obvious until you start looking into it. I had assumed that I could get the latest Ubuntu image (Bionic 18.04) and install the lastest ROS distibution (Melodic).

Ubuntu MATE & ROS Kinetic on a Raspberry Pi 3B+?

As I understand it; Ubuntu MATE (16.04) is available for RPi2 and RPi3 but not the B+ and ROS Kinetic is available for Ubuntu Xenial 16.04 on the "armhf" architecture (Pi), but not for Debian-armhf. The latest ROS Melodic only supports Ubuntu Bionic. Kinetic is supported until April 2021, so shouldn't be a problem, but there's no Xenial/16.04 image for the Raspberry Pi 3B+. Xenial's support ends April 2019, Bionic/18.04 ends April 2023. So Bionic for armhf would be the better choice, if it existed...

See https://droidbot07.blogspot.com/2018/10/ros-on-raspberry-pi-3b.html for details.