In newer releases of Red Hat and CentOS, version 8 and above currently, there is no libssh2 developer package provided.
To use libssh2 you must enable the EPEL repo. After that libssh2-devel can be installed
If development is needed on the platform then use the libssh2-devel package
> sudo yum install epel-release > sudo yum install libssh2-devel
If development is not needed on the platform then use the libssh2 package
> sudo yum install epel-release > sudo yum install libssh2
If the above solutions do not work, you can download the libssh2 source tarball from https://www.libssh2.org/
and then run the following commands (assuming the libssh2-1.10.0.tar.gz tarball is in the Downloads folder of your system):
> cd ~/Downloads > tar -xvf libssh2-1.10.0.tar.gz > cd libssh2-1.10.0 > ./configure > make > sudo make install