Hi there,
It seems there is an issue with the pypi manifest (?)
The changes for tag v2.1.0 ( 14be68ade2618595bcef123f91a0f0e92d8bef4bc ) inlcuded "Relax historical constraints" #413 but it seems the dependency changes weren't translated to the setup.py
Straight from the pypi json :

42 "dash-bootstrap-components (<1)",
This doesn't reflect the changes made in 2.1.0, unless I'm missing something
(should be:)
42 "dash-bootstrap-components",