I wrote a tool to make it even easier to download programs to the micro:bit. It's called Microflash and it means when you activate a .hex file you can download that to a micro:bit with just one more click.
To install on an Ubuntu 18.04 LTS machine enter the following in a terminal:
$ sudo apt-add-repository ppa:robert-ancell/microflash-stable
$ sudo apt install microflash
It's open source (GPL-3) and you can contribute on the GitHub page.
You can also help translate it into your language.
I've packaged it for Ubuntu, but you should be able to compile / package it for other Linux distributions.
If it's so easy why make a tool? Well, there's easy and then there's easy. There's two main reasons:
There's actually quite a number of steps the operating system makes you go through before you get the file to the micro:bit. This is on Ubuntu but it's pretty similar on ChromeOS / Apple / PCs.
Once you have your program ready, you click the big "Download" button in the bottom left.
This downloads to your computer and shows up in the bottom bar in Chrome (similar in Firefox). You need to find the file on your computer, which is most easily down by clicking the small up arrow beside it (quite a small click target).
Select "Show in folder" from the menu.
This opens your file browser, and from there you drag it into the MICROBIT folder.
It's four clicks in total which is not too bad, but still a bit of a chore if you do it a lot or you're not super experienced in all these operations. With Microflash you just click twice - once on the Download button and the the Flash button in Microflash. And if you've forgotten to connect the micro:bit that's shown too.
Microflash avoids another problem too - flashing an older version by accident. Each time you download the program it has the same filename. The browser adds a number the end when it saves it but it's quite hard to work out which was the most recently downloaded version. When presented with the following I've observed people dragging the wrong version onto their micro:bit.
I hope you find this tool useful!