It seems to work with all the popular calendars.
I can understand wanting to get away from Google Calendar.
We have discussed having a public identity, a business facing identity where you use services which we all are trying to avoid.
My employer uses Microsoft office which I am thankful I do not have to use the calendar. My professional work life is compartmentalized from my home private life, as well as I feel is necessary to be at peace. If I had to interact with the calendar, having an open source “front end” would be an option I would look for.
I mentioned I have a friend who is a nurse and the ability for others to see her calendar to know if she is available to work or not would be a financial benefit, not counting the time she would spend jumping in several popular calendar apps to manage work schedules.