Using iCalendar RRULE Repeater Options (BETA)
There is undocumented feature in the repeater that is still in beta allowing you more complicated repeating options, but you can use it successfully.
Go to the event and click Set Repeater button and this popup will show up:
Now the option I will give you is quicker, but as I said undocumented yet. Click on the popup (anywhere also the form should be rested no checks or options selected) and press CTRL + ALT + SHIFT+ R and the popup will change into this:
In the first input RRULE String paste the RRULE generated from this website: https://icalendar.org/rrule-tool.html