WIDGETS: how can i find widgets for Mac OS 10.12.6 Sierra?

Several years ago, there used to be a widgets site on Apple.com that would allow you to see the various Dashboard widgets by category, update, or download them. That site is gone, as is Apple's interest in those old web-based widgets whose developers have long since moved on to other things.

Widgets have not been updated for several years. They used to be part of the old Dashboard. They effectively are independent web pages treated as temporary apps.