Thank you, Lilith.
The only reverb that I had for Reaper (native Linux VST or JS--I'm not using WINE and Reaper can't use LV2) that I really liked, prior to Dragonfly, was the included impulse loader ReaVerb. I'd found some really nice impulse files, got my favorite reverb sounds to date, and was satisfied that I could use Linux for audio without compromise. Hearing the latest version of Dragonfly, and having it sound better than the impulses I already thought were the best reverb I'd used, that's pretty awesome.
The ProG plugin of Freeverb3 was my favorite of the Freeverb3 package, and I'd spent a lot of time comparing it with Hibiki. I wonder now if I missed some settings in Hibiki, or was confused by the interface (while somehow being able to get great sounds with ProG?) Also Is Hibiki capable of the 10s decay length of Dragonfly?
A note to anyone using Dragonfly and wanting the high end to be buttery smooth but also not just "cut off"/dark: try Airwindows "Lowpass". It's no regular lowpass.
PS. someone had posted a link to this video of Eventide UltraReverb
on the Reaper forums (in a discussion about plate reverbs). I took the audio from that clip, put it in Reaper, separated the wet examples from the dry examples (put them on separate tracks), and then put Dragonfly on the track with the dry examples. I was able to mimic all of the sounds of that reverb with Dragonfly, except the most extreme ones (the ones with distortion, delay, or "infinite decay" due to lots of feedback)...and I'm reasonably certain I could mimic those too, by using other plugins in series for the delay/distortion/compression.