Maybe take a look at FluidCalendar, I just found it but haven’t tested yet : https://github.com/dotnetfactory/fluid-calendar It’s still in early development but it may have what you need.

Alternatively, you can take a look at Baikal for CalDAV and CardDAV support : https://github.com/sabre-io/Baikal

If the file doesn’t exceed 2 GB, you can use this : https://lufi.ethibox.fr/ Files are encrypted and cannot be seen by the owner of the website and the share can only go up to 30 days. It is recommended by Framasoft, the ones behind peertube.