I can’t activate RPR 2.0.94 on B3D 2.80 RC. It doesn't show up on the add-on list. On MacBook Pro 15" Radeon Pro 560 4 GB.
On B3D 2.79b it works perfectly.
Before install RPR 2.0.94 I've uninstalled all the version.
The experimental "Nightly" build of 2.80 is not code signed the same as the RC1 build is.
Unfortunately, as you correctly point out the Brecht version and the subsequent official RC1 build for macOS still do not fix the problem for v2.0.94 of RPR.
I get the same error as you.
There is one known way around this issue.... disable SIP on macOS. However... that is not really advisable but it does prove this is a code signing issue at Blender's end.
Today I quickly tried the BRC 3 and again RPR 2.0.94 it didn't work (same problem as above), then I downloaded the experimental Blender build and it worked. If the final Blender release is going to be like the RC I think it's a problem for RPR.