boost:pfr::io insertion into std::cout works, but std::stringstream does not?

https://cppcoach.godbolt.org/z/Mocb7znYf

Only only does it not allow to stream into std::ostream / std::stringstream but also makes it "not play nice with {fmt}".
see https://github.com/fmtlib/fmt/issues/3245

in the meantime, how do I work around this?

Start with the linked Compiler Explorer reproduction and compare insertion into std::cout with std::ostream and std::stringstream. Review the related fmt issue to understand the reported incompatibility, then identify the expected streaming behavior and document a confirmed workaround or precise fix scope.

Written by the indexing model from the issue text.