The pinning of FFI to 1.9.18 done in
PUP-8438 is slightly problematic as it means that Puppet cannot be run on Ruby 2.5. This is also causing some issues coordinating FFI versions with PDK and the ubergems like https://rubygems.org/gems/puppet-module-win-default-r2.4
There was initially some concern over the new gems as described in https://github.com/puppetlabs/puppet/commit/d10b21f09107846d03fd8e2df6128f967207366c
This ticket should validate the latest FFI, pick a minimum version, and bump the version in puppet-agent in addition to Puppet repo itself.