Currently, we ship an `override.ini` that contains only `EnableProfileMigrator=0`, and only on macOS. It disables the migration from other browser (as stated, for example, [here](https://bugzilla.mozilla.org/show_bug.cgi?id=1396996#c0)): > EnableProfileMigrator is about displaying the migration from other browsers at startup. So, I'm inclined to see it as something desirable for all our browsers. I think it is triggered when creating the profile, so only on macOS at the moment (I've tried to rename my profile directory, and remove the `override.ini`, but it didn't show me the prompt to migrate from other browsers...). I haven't really checked what the migration does (e.g., if it only imports bookmarks), but the idea of keeping the browsers distinct is good, in my opinion. In any case, even with `EnableProfileMigrator` set to `0`, the menu item to import bookmarks from other browsers remain available (I've tested on Linux, at the moment, because I cannot test on macOS at the moment). In any case, we could disable the migrator at build time, too, with `MOZ_PROFILE_MIGRATOR` (in `browser/confvars.sh`). I prefer this solution, because it's yet another thing moved from the build repository to this one.