Are you on AlmaLinux or something else? subscription-manager should not be in play at all on AlmaLinux.
You probably need to enable the `CRB` repo as that's where the package exists.
You can do this with `sudo dnf config-manager --enable crb`
[jonathan@jon-home ~]$ dnf info libnghttp2-devel
Last metadata expiration check: 0:00:06 ago on Mon 19 May 2025 09:34:07 AM CDT.
Available Packages
Name : libnghttp2-devel
Version : 1.43.0
Release : 6.el9
Architecture : i686
Size : 52 k
Source : nghttp2-1.43.0-6.el9.src.rpm
Repository : crb
Summary : Files needed for building applications with libnghttp2
URL : https://nghttp2.org/
License : MIT
Description : The libnghttp2-devel package includes libraries and header files needed
: for building applications with libnghttp2.
Name : libnghttp2-devel
Version : 1.43.0
Release : 6.el9
Architecture : x86_64
Size : 52 k
Source : nghttp2-1.43.0-6.el9.src.rpm
Repository : crb
Summary : Files needed for building applications with libnghttp2
URL : https://nghttp2.org/
License : MIT
Description : The libnghttp2-devel package includes libraries and header files needed
: for building applications with libnghttp2.
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dnf config-manager --enable crb
Updating Subscription Management repositories.
Unable to read consumer identity
This system is not registered with an entitlement server. You can use subscription-manager to register.
The above is what I get....
Jerry
--
Jonathan Wright
AlmaLinux OS Foundation
Yes..
more /etc/os-release
NAME="AlmaLinux"
VERSION="9.5 (Teal Serval)"
ID="almalinux"
ID_LIKE="rhel centos fedora"
VERSION_ID="9.5"
PLATFORM_ID="platform:el9"
PRETTY_NAME="AlmaLinux 9.5 (Teal Serval)"
ANSI_COLOR="0;34"
LOGO="fedora-logo-icon"
CPE_NAME="cpe:/o:almalinux:almalinux:9::baseos"
HOME_URL="
https://almalinux.org/"
DOCUMENTATION_URL="
https://wiki.almalinux.org/"
BUG_REPORT_URL="
https://bugs.almalinux.org/"
ALMALINUX_MANTISBT_PROJECT="AlmaLinux-9"
ALMALINUX_MANTISBT_PROJECT_VERSION="9.5"
REDHAT_SUPPORT_PRODUCT="AlmaLinux"
REDHAT_SUPPORT_PRODUCT_VERSION="9.5"
SUPPORT_END=2032-06-01