Thanks for reviving this topic!
I had a couple of runs at converting and gave up. In time, as I moved to an M1 Mac, I lost my Discourse testbed and never got around to recreating it. I hope to return to this project as soon as I have some time to spare. Dealing with redirection of existing links was a piece I was struggling with. I had not gotten around to verifying all the BBCode was translated correctly. I have 130K+ posts to convert which is daunting to verify.