Elastic Beanstalk - yum does not have package available - Python 3.9 AL2023 version 4.1.3

Hello.

This is a fairly old stackoverflow answer, but a similar question was asked.
Apparently, when I try to install "libffi-devel" with yum, "libjpeg-turbo-devel" is installed instead.
https://stackoverflow.com/questions/25860084/error-trying-to-install-libjpeg-devel-with-elastic-beanstalk

Indeed, when I started Amazon Linux 2023 with my AWS account and checked, "libjpeg-turbo-devel" was installed.

[root@ip-172-31-38-40 ~]# yum install libjpeg-devel
Last metadata expiration check: 0:02:25 ago on Thu Aug 15 00:04:41 2024.
Dependencies resolved.
==================================================================================================================================================================================================================
 Package                                                Architecture                              Version                                                    Repository                                      Size
==================================================================================================================================================================================================================
Installing:
 libjpeg-turbo-devel                                    x86_64                                    2.1.4-2.amzn2023.0.5                                       amazonlinux                                     99 k
Installing dependencies:
 cmake-filesystem                                       x86_64                                    3.22.2-1.amzn2023.0.4                                      amazonlinux                                     16 k
 libjpeg-turbo                                          x86_64                                    2.1.4-2.amzn2023.0.5                                       amazonlinux                                    190 k

Transaction Summary
==================================================================================================================================================================================================================
Install  3 Packages

Total download size: 305 k
Installed size: 1.0 M
Is this ok [y/N]:

I was able to resolve this!

I SSHd into the EC2 instance created by Elastic Beanstalk. From there, I tried to install the package manually, but it also failed with a more informative 403: Forbidden for any yum-related commands to the Amazon Linux 2023 repos. It turns out I had a S3 VPC Endpoint policy set up to allow connections to the repos for the previous versions of Amazon Linux, but I hadn't updated them for Amazon Linux 2023. After I adjusted the endpoint policy, I was able to install the package successfully.

It seems the deployment utilities catch the installation error but return a much more generic description of 'Unable to install', when the actual text of the error message would have been very helpful.