Interesting project ... and now here's some constructive criticism, obviously meant in good faith for possible improvements.
Pertains to the website, since I haven't tried the Android app yet.
1. Sometimes downloading seems to be slow / down / overloaded servers, not sure what's the actual cause, but tried it with and without a download manager using Chrome.
2. Firmware availability limitation in SamFirm / Samsung Server seems to be also present here (ex. SM-G930A / G935A unavailable). Suppose not much can be done about it since Samsung is simply not serving it up.
3. Would be helpful to have each file designated as HOME or FACTORY depending on the type of firmware package. Factory version is much more preferred/useful.
Overall a great looking, and informative website.
'tsit for now,