Thanks for the answer and the plugin.
Yes, I did try it. It is simple and it works. I put something as URL like https://localhost/somewhere/calender.ics.
This method is of course not very fast because the complete ics-file is handled every time you display the calender. I assume you try to speed up things a little by reading the downloading the ics-file end write it on the local filesystem. A kind of simple cache. Which is useless in this case because the ics-file is already local and up to date. I don’t see any performance gain with copying the ics-file to a cache.
So what I wanted to ask is: can I prevent the the copy to the cache or can I configure my local ics-file as cache file. In fact I would like the plug-in to read my ics-file directly.
It solves also the delay of showing the calender updates.