Maybe I’m missing something. I don’t have a use for ARC now, so have not installed it.
However, I was able to update to Roon 2.0 on my iMac, iPhone and iPad. First I updated the iMac. When I opened the app in either the iPhone or iPad, there was a message indicating the latest version on Roon core and provided a link to update the mobile apps. No problems for mac users.