Looking at your system diagnostics, your phone is stuck because of a version mismatch. Your Mac mini runs legacy Roon 1.8, while your iPhone is on Roon 2.0+.
Roon 1.8 Legacy is no longer supported and the remote apps are unavailable. You must update your Mac mini to the current Roon version.
Your Mac mini (Late 2014) runs macOS 10.12.6. As of the Roon 2.65 update, Roon Server requires macOS 12 or later. Your Mac mini hardware natively supports macOS 12 Monterey.
Update your Mac mini to macOS 12 (Monterey).
Download and install the current Roon Server software from our website.
Open the Roon app on your iPhone; it will connect automatically once the server is updated.