Although 3CX has stopped development of the standalone Mac client, the latest version (although now a bit outdated) still works and is downloadable here:
Here's a list of direct download links to the latest macOS installers. They are all links to Apple's servers, either direct links to the App Store, or, in case of older versions, links to Apple's CDN.
Direct links to App Store:
Older versions are only available as DMG files from Apple's CDN:
If you ever need to perform connectivity troubleshooting and need to see whether a Dell server's iDRAC can reach a certain IP, you can use the iDRAC diagnostics command function to perform a "ping":