Seeing this too! Can't even access the Add-on section of the preferences panel. My guess is that this is macOS-related, but this renders the RC unusable.
Jul 12 2019
Apr 2 2019
This is now fixed for me with the latest 2.8 daily build. I did update macOS to the latest dev version so it's possible that fixed it on the platform side, not sure.
Mar 25 2019
For what it’s worth, I’ve tested with two eGPUs: Radeon RX 580 (8 GB) and Vega 64 (8 GB). Issue behaves the same.