PUP-7808 changed puppet resource <type> --to_yaml so that it emits structured data correctly, using pops serialization. One unintended side-effect is that any module whose instances method returns resources whose values are the result of executed commands (via Puppet::Util::Execution.execute or the commands provider framework) will be emitted as:
While it is technically valid YAML, it is not parseable if the puppet classes aren't loaded or tags aren't stripped.
We will fix puppet in PUP-10105 to not emit ProcessOutput classes (and likely warn).
But the mysql module should call ProcessOutput#to_s when creating resources. I think this could be handled when calling mysql_raw(...).to_s in https://github.com/puppetlabs/puppetlabs-mysql/blob/ab9292eab45e81e693738e93f0eaf55d9bfd7752/lib/puppet/provider/mysql.rb#L100-L118