Apple equivalent for Excel data and iPhone connectivity

Apple's Numbers is a free spreadsheet application, but it is not a clone of MS Excel. As KiltedTim inferred, if your Excel spreadsheets depend upon Visual Basic (e.g. VBA) or Excel-specific functions, then Numbers may not be the cross-platform solution you require.

Consider testing Collabora Office for Desktop Classic which is available on macOS and Collabora Office for Mobile available for i/Pad/OS from the respective Apple stores. It shares a great deal of functionality with the current LibreOffice Suite and that MS clone nature may be the cross-platform solution you seek. Test is the keyword here as I do not use Collabora and cannot vouch for it for your solution need.

Numbers is Apple's spreadsheet application. Depending on how complex your workbooks are, it should serve the purpose. There are several open source office suites out there as well if you prefer.

LibreOffice is compatible with your existing Excel files - including Macros - and is very similar to Excel in looks and usage.