Looking for a simple 'Countdown / Days Until' Calendar Card

Hi! I’m in the process of moving 10 years of work in another platform to HA, trying to spend as little time as possible creating code/yaml from scratch as the to do list is long.

One of the first things I am trying to do is get a ‘Countdown Card’ for significant calendar events displayed on the dashboard, ideally with a background image. Like this:

I’ve found this thread, which is a little older and requires some navigating of GitHub issues and one dead link that sounded promising.

I worry about trying to apply code from old threads as it often leads to learning that something changed in the core system that I have to figure out. I’ve spent more time searching than I care to admit. Do I need Mushroom? I didn’t see a good example while skimming those threads.
Can someone point me to a good solution?