Even though gpgme-devel requires libassuan-devel: $ pkg-config --cflags --libs gpgme -I/usr/include/libassuan2 -lgpgme -lgpg-error -lassuan ... there's no RPM dependency between them. This is because we have a downstream patch to remove the 'Requires' from gpgme.pc and gpgme-glib.pc (bug 1953905), and hence RPM doesn't automatically add the dependency.
Note that this affects only RHEL 8. RHEL 9 is fine.