Has kernel version 5.14.0-503.38.1.el9_5 been discontinued? If not, which repository is it currently available in?
That kernel is the second newest in AlmaLinux 9.5 BaseOS repository.
The AlmaLinux 9.6 is now out. Therefore, the baseos on repos does now have el9_6 kernels (only 5.14.0-570.12.1.el9_6 so far). The mirrors may still hold the el9_5 content, but it will soonish move to AlmaLinux vault.
You should be able to get URLs to nearest mirrors from https://mirrors.almalinux.org/mirrorlist/9.5/baseos
Note that el9_5 content is no longer supported, since el9_6 is out. (Likewise, the 5.14.0-503.40.1.el9_5 did supercede the 5.14.0-503.38.1.el9_5.)