While updating

That is a pretty clear error, and how to solve it, I thought. Great. So I ran the command:

view plain print about
1ng add @angular/localize

At my console, and was surprised at the response:

NG Bootstrap thinks that it needs this new library to be added. Angular thinks it is already installed. What happened?

When Angular 15 came out, they removed the polyfills file entirely. Polyfills are now added in the Angular.json file. I had to set up the localize polyfill manually.

Open up Angular.json file in the root of your project, and search for polyfills. You should find them at project.myproject.architect.build.options, and it probably looks something like this:

view plain print about
1"polyfills": [
2 "zone.js"

Just add your new polyfill:

view plain print about
1"polyfills": [
2 "zone.js",
3 "@angular/localize/init"

Restart your Angular CLI and you will be off to the races.