Because they are no longer bundled, you must source the files separately if you want the classic Bootstrap 3 look.
However, you can still use Glyphicons in Bootstrap 4 by manually adding them or, more commonly, switching to a modern alternative. 1. How to "Download" and Use Glyphicons in Bootstrap 4 glyphicon bootstrap 4 download
If you are looking to download for Bootstrap 4 , it is important to note that Glyphicons were officially dropped from the core Bootstrap framework starting with version 4.0. Unlike Bootstrap 3, which included them by default, Bootstrap 4 was built to be more lightweight and allows developers to choose their own icon libraries. Because they are no longer bundled, you must
GitHub - Darkseal/bootstrap4-glyphicons: How use Glyphicons with Bootstrap 4 (without getting mad) Because they are no longer bundled