I just restored my SD card dump and the LibreELEC addon server (now again?) has the 9.0 addons for 905 ( addons.xml.gz ).
However, in your most recent build (RR-20190326-8c1b004) it's version 9.1 and that is not on the server currently.
I just wanted to say that the box has some serious real estate, hence it's nowhere sold at such low prices as $25. DVB tuner, lots of RAM, Bluetooth, etc. plays even Quake and all sorts of games. And that doesn't change as the box gets older! It even runs Openload videos 1080p inside Firefox on Android and ARMbian (but of course not LibreELEC). It would be a shame if it turns out broken, just because someone deleted the less pretty files on their server and no one bothered to mirror it.
If I could I would use Android, just for the browser. But the internal NAND is corrupted. That is how I happened to install LibreELEC on the first place. Android on the other hand however doesn't at all work properly with retro gaming. So I feel I have gained more than I lost.