Can I use the Tiller Web App on an Apple Mac desktop

Can I use Tiller web app on my desktop which is an older Apple MAC with an Intel Core I5 and 8 GB of memory and 1 TB of storage

As long as it can run Google Sheets, which I believe that computer should be able to, you should be fine with the Google Sheets version. On the Excel side, you’d have to look into Excel’s requirements since you’ll need a newish version of Excel to work properly.