This convinced me to never use Arc again. I created a small guide to migrate from it to an open-source alternative: https://gist.github.com/clouedoc/4acc8355782f394152d8ce19cea...
TL;DR: it's not possible to export data from Arc, but it's possible to copy-paste the folder to a Chrome profile, and Firefox and other browsers will detect&import it.
I was literally using Arc because of the ability to hide most of the userchrome.
Every time I open split views or tabs I curse. I've said this in the past but layering view multiplexors has to be the most stupid modern "super-user" trap. You have the ability to open multiple browser windows and composite them side by side, use it.
Does anyone know of any other browsers that are chromium based and have very little features aside the ability to hide most of the UI?
I also wrote a guide on ARC features that work better on Firefox: https://thannymack.com/#Arc%20features%20that%20work%20bette...
Unfortunately, Zen Browser simply isn't an alternative. If you like Arc, then Zen's UI for tabs and splitting views isn't really anywhere close to satisfying the same needs.