I realize it's been few months, but I will post this anyway. As I also recently went through the same ordeal.
Thanks to OP for posting an easy to follow guide.
I found the official install instructions at OpenHAB quite good: https://www.openhab.org/docs/installation/linux.html
...with one exception. Currently, it seems there is some bug going on with their build system or something. I actually had lodged an issue of my own (and even had submitted a PR to correct the documentation) before someone replied, pointing me to the root issue. So for the time being, instead of using https://dl.bintray.com/openhab/apt-repo2 location, you should use https://openhab.jfrog.io/openhab/openhab-linuxpkg repository location.
Further, if you care about issues such as software freedom (which I do a great deal) you might want to consider installing Azul/Zulu Java 8 (make sure it's 8!) which I have done, instead of Oracle Java. Azul's (also excellent) instructions can be found linked from the OpenHAB Linux install instructions. And that would also solve your missing repo problem, obviously.