I made this simple tool to load .ics files client-side and open it in-browser so Apple's iCal integration enables adding it to their calendar.
To say the app is barebones is an understatement: I made it in 2 minutes. Visual enhancements might come.
Source: https://github.com/VladCuciureanu/iCalHelper
Useful context: https://news.ycombinator.com/item?id=36116650