Hello, thanks for Tonelib GFX, it's really great and performs well for me on Fedora with Reaper as a VST, or at least 3.9.0 does. The 3.9.9 version doesn't display correctly in Reaper's VST window.
It's Reaper 5.983 for Linux, which is the latest from the Reaper website. I should note that I'm running Reaper on a dedicated box with no desktop environment and I'm remoting the GUI over a 1Gb ethernet link to my laptop. I have both versions of the Tonelib VST in Reaper and I put one of each version on a track to take the posted screenshots, so the only difference should be with the Tonelib VST and not anything else in the environment.
Newest version still isn't displaying correctly for me. 3.9.0 works fine, everything after is wonky. This is with X11 forwarding.