I need to install libmysqlclient-dev but get No match for argument: libmysqlclient-dev Error: Unable to find a match: libmysqlclient-dev.
Because you are using a debian package name
You probably need mysql-devel (or mariadb-devel)
What says so?
RPM-packages built to work in AlmaLinux do not require debian packages.
(To build) source code does not require packages by name at all, it wants headers (for compiler) and libraries (for linker).
Ideally, one does find the desired application as RPM-package and dnf pulls in dependencies “auto-magickally”.