Hey Grant, I'm getting this same issue in both Wineskin and CrossOver.
Would it be worth uploading the cncnet.log as suggested in the error message?
I tried to follow your suggestion involving the TS version and copying over the YR stuff, but I couldn't get it to work unfortunately.
I installed the TS version and was able to get in to the lobby and even join games (even though I don't have TS). I then copied my already installed YR folder to the 'Games' Folder, along with the YR CnCNet installer. I then launched from the YR CnCNet .exe. After installing, the initial YR menu window loads, but when I click 'CnCNet', where I should be prompted to enter a nickname before joining the lobby, I get the error message attached.
Have I possibly done something wrong or does it seem like this approach is not viable?