Now we can see the actual error:

This is happening because m2r2 depends on mistune, but mistune 3.0+ removed the BlockGrammar class. Let's pin both mistune and m2r2 to compatible versions:
requirements.txt
Key changes:
Added mistune<3.0 to use a version that still has the BlockGrammar class
Kept other version pins the same
Reordered requirements to ensure mistune is installed before m2r2
This combination should resolve the dependency chain:
sphinx < 7.0 (for docutils compatibility)
docutils == 0.16 (for reprunicode)
mistune < 3.0 (for BlockGrammar)
m2r2 == 0.2.7 (known working version)

docs/requirements.txt

@@ -1,8 +1,9 @@
 sphinx<7.0
 docutils==0.16
+mistune<3.0
+m2r2==0.2.7
 -e .
 numpydoc
-m2r2==0.2.7
 sphinxcontrib.mermaid
 sphinx_rtd_theme<1.0
 sphinxcontrib-apidoc