Hello!,
My Nucleus is not reachable from outside. In local network everything is ok. I have a static IP if needed, but I don’t know how to make access.
both. I have country house and apartment for example. I need to connect to nucleus from both locations.
and arc doest connect out from local network too
By design, the Roon Core (in your case, this is running on your Nucleus) is only accessible by Roon Clients and Roon Remotes when they are all in the same local network - Roon will not span across subnets.
Some people use VPNs to overcome this, but use of VPNs is not officially supported by Roon Labs. Search through the forum to find the discussions about VPNs and setting them up.
Roon ARC is a completely new app designed to access a Roon Core from remote locations, i.e. outside of your home network. You need to set up access to your Roon Core by going to Settings > Roon ARC in Roon