They updated Arc shortly after that. I have uBlock Origin working just fine on the latest Arc. I also tried moving to Zen, but it lacks too many features and looks horrendous compared to Arc.
It's seriously annoying because Arc has been just perfect for the kind of "keep each hat separate" workflows I have going. SigmaOS is the closest other thing I've used to it, but its reliance on a weird amalgam of the Safari and Chromium engines makes it behave really oddly with plugins like 1Password.