Outside from home I can access Roon Core via Phone, but not via PC?

[Suedkiez (Just a fellow user like you)]

The only thing you are missing is that the ARC app only exists for iPhone/iPad and Android devices. There is no PC version. And using ARC outside from home requires the ARC app.

When at work, you could, e.g., attach an external DAC to the phone.

The feature suggestion for a ARC app for PC is here - you can add your vote:

Roon ARC for Desktop / Laptop (Windows, Mac, Linux)

Roon ARC should have a desktop version so it can be used on Windows, Mac, Linux while out of home. This connectivity is achievable with a tool such as ZeroTier, but a ‘native’ solution would be much easier for all. I’ve read in other posts that this is not on the roadmap, can Roon provide their reasoning behind that decision?

Alternatively, you could rig something up to use the full Roon app on the PC when at work, using some VPN solution like ZeroTier or something. See the Tinkering section.