These widgets have been edited by me to make them look great on macOS Big Sur. They use the SF Pro Display font. Again, they're edited to my liking so 1) I'm not guaranteeing they'll work for you out of the box and 2) I am not claiming this as my work. These were originally developed by other people and I've reworked them to the point that I like them and they work for me. Despite that, I think both of these widgets are very nice and should be reasonably easy to setup.
You'll need Übersicht for these widgets to work! Link provided below.

What does it look like?

Check out the tweet linked below to see what my setup looks like. The date part of the date and time widget is not shown as only one is shown at a time.

I like showing off my desktop widgets but I don't think I've done it here yet, this is done with Übersicht! pic.twitter.com/GhkpsCO887

— Tyler Dakin (@_tylerdakin) September 14, 2020

Time and Date Widget

All that should be needed for this widget is the widget engine, Übersicht, provided below. For each widget, just put the uncompressed folder into the Übersicht Widgets folder. To view the date instead of the time, simply click once on the time. Do the same on the date to switch back to the time.

Download Original Source

Music Widget

This widget works with the music app to display the current song being played. I changed the script file for my personal use, but I've changed it back for you so it should be ready to go.

Download Original Source

Übersicht Widget Engine

Use this application to view and use the widgets.

Download Übersicht