Slack - Follow these instructions
This appears to have solved my issue with initializing communication bridge, this is on Catalina through the default OSRS client.
Hope it helps someone else as well.
Spectre was able to open the OSRS client, and I have selected Alpha Fighter which currently has Spectre support.
when I click Start Instance after all steps are finished, I get the above error.
edit: solved. install RM in a non-system drive (one where you don't need permission to make changes...
