Hi @KHenderson ,
Have you add a Calendar screen in your canvas app?
Do you want the Calendar control to be populated with events from your SP Calendar List rather than Outlook events?
Based on the needs that you mentioned, I think the Calendar screen could achieve your needs. Firstly, please add your SP Calendar List as data source into your canvas app.
I have made a test on my side, please take a try with the following workaround:

Set the Items property of the CalendarEventsGallery1 to following:
/*Shows events only on selected date*/
SortByColumns(Filter('Your SP Calendar List', Text('Start Time', DateTimeFormat.ShortDate) = Text(_dateSelected, DateTimeFormat.ShortDate)), "EventDate")
Within the Events Gallery, re-reference the column value from your SP Calendar List in these Labels.
Set the Visible property of the Circle1 under the MonthDayGallery1 to following:
/*Visible if calendar events are found on this day*/
CountRows(Filter('Your SP Calendar List', DateValue(Text('Start Time')) = DateAdd(_firstDayInView,ThisItem.Value,Days))) > 0 && !Subcircle1.Visible && Title2.Visible
Please consider take a try with above solution, then check if the issue is solved. You could also refer to the sample app I attached below.
Best regards,