The environment variable you're thinking of is `PYTHONUNBUFFERED`, not `UNBUFFERED` [0]. If you want a generic solution to this problem, try the `unbuffer` command [1].
For anyone who's interested, I recommend reading Julia Evan's article [2] about this problem and its solutions.
FWIW, I'd accept either one. Some names don't take an extra s by convention, like Jesus, but otherwise it seems in practice that names that feel like plurals don't get it. I'd write "Jess's" but "Jenkins'".
(I consider myself a follower of Lynne Truss's, and have deliberately not considered a grammar reference for this answer, as I'm sure this is within the interested reader's ability and shan't spoil these readers' fun.)
For anyone who's interested, I recommend reading Julia Evan's article [2] about this problem and its solutions.
[0]: https://docs.python.org/3/using/cmdline.html#envvar-PYTHONUN...
[1]: https://manpages.ubuntu.com/manpages/noble/man1/unbuffer.1.h...
[2]: https://jvns.ca/blog/2024/11/29/why-pipes-get-stuck-bufferin...