This is a PSA that no-bs-countdown exists and is ready to be used. It is literally the simplest React countdown possible with no ads and all the personalisaion that is necessary. I got annoyed with how needlessly complicated and ad-filled online countdowns are. This one is customizable and simple (there's also no tracking). The URL can be shared too, I personally have my startup pages set to a countdown I configured.
The code is available here (GitHub). It is hosted using GitHub Pages.