Can we get Reaper as PluginHostType under Linux?
Looking at the source code for juce_PluginHostType.cpp it looks like it wouldn’t be too hard to write a function that checks the host type even if it’s not in the PluginHostType list 
It looks like all you really need is:
juce::String hostPath = juce::File::getSpecialLocation (juce::File::hostApplicationPath).getFullPathName();
juce::String hostFilename = juce::File (hostPath).getFileName();
I don’t have Reaper but I tested it in MusE (also not on the PluginHostType list) in Ubuntu and I was able to get “muse” to print to the console by just calling DBG(hostFilename) after that bit of code
Would be great if JUCE just returned the hostFilename instead of returning “Unknown” though