OSX: Adding FL Studio as ReWire client renders as a black screen

If I add FL Studio (20.6) as ReWire plugin to a Renoise (3.2.1) project on MacOS (high sierra - mojave didn’t actually have anything worth upgrading for DAW wise, and catalina would literally make tens of thousands of dollars worth of VST instruments and effects stop working so… high sierra it is), it starts up as a black screen, with only the rewire dialog visible:

I asked about this on the FL Studio support subforum, and their engineer said “[I] assume this is Renoise that fails to render in this case. Could you contact the Renoise developers about this?” hence this bug report.

Clicking the fruit logo (which toggles between host and client) causes a rerender, so it’s not impossible to work with, but I didn’t even know you could click that until their devs pointed it out, and had redone my entire Renoise project in FL Studio just so I could get a single synth solo with midi automation added into my track before I leanred I could just… click somewhere instead =S