Hello Viorel:

I can't reproduce this with the current development head when running:

====
python3 -m pytest -k "markdown2 and test_markdown_hyperlinked_url" test
..
test/test_templating.py::Markdown2TestCase::test_markdown_hyperlinked_url PASSED [100%]
...
_______________ Markdown2TestCase.test_markdown_hyperlinked_url ________________
----------------------------- Captured stdout call -----------------------------
<p><a href="http://example.com/" rel="nofollow noopener">http://example.com/</a></p>
===

With Python 3.8.10. But this same test has been passing in CI with both
3.11 and 3.12 and markdown2 <= 2.4.8

I ran it on my dev system with markdown2 version:

   python3 -c 'import markdown2; print(markdown2.__version__)'
   2.4.12

I also upgraded markdown2 to 2.4.13 and it still passes.

What version of markdown2 are you using?
What version of Roundup are you using?

It's possible something breaks with markdown 2.4.9+ and newer Python.
It's also possible it's fixed in devel (2.4.0 beta next month).

The markdown2 limitation has been lifted (needed a bug fix in markdown2),
so CI is running 3.11 and 3.12 with the newest 2.4.13 version as I type.