Wanted to confirm that the solution from @brc27 is the best one so far. It's the Calendar Flyout app in the Microsoft Store (https://www.microsoft.com/store/productId/9P2B3PLJXH3V) even if it does cost $1.70. But wanted to give a couple of tips if you go that route:
It does in fact only sync to your Windows Calendar, which initially shows only events from your microsoft account, but that's OK because you can sync your Windows Calendar to other accounts like Google or other Outlook/Office 365 accounts, and then those will show up on Calendar Flyout. I synced two separate business Office 365 calendars and my Google calendar this way. From the Windows Calendar app, click on hamburger (to show the sidebar) > Settings Icon > Manage Accounts > Add the accounts you want.
In my case, I did not want all my emails or contacts from these other accounts in the the Windows email app, just my calendars, so that Calendar Flyout could show them. And so I had to take another step to unsync the mail/contacts. Follow these instructions:
https://answers.microsoft.com/en-us/windows/forum/all/sync-only-calendar-data-in-my-google-account-w...
FINAL STEP: To bring Calendar Flyout into the system tray so it's always visible, you need to pin it in your system tray. When the app runs, it's already in the system tray, but you need to exapnd the system tray, grab the Calendar Flyout icon, then drag it to the taskbar portion of the tray. Below is a GIF to demonstrate. Also, be sure your settings on Calendar Flyout are set to Run at Startup. You can also setup a keyboard shortcut in its settings.
@Everyone
The calendar works just fine in win 11. Pin to task bar for ease of use. change settings in Settings/Apps and the notifications appear in the bottom right corner as it does in previous versions.
