Jupyter notebooks html tags not rendering well

I use Brave browser for my jupyter notebook (not jupyterlab) works under Amazon Sagemaker, but I also use Chrome for my Internet activities, so last week the update symbol appeared on Chrome, so I updated it, and inmediately my notebooks on Brave stopped rendering well the following tag <hr style="border:3px solid black"> </hr>, which shows a thick straight line that I use to separate blocks of cells in a markdown cell, is now rendered as a thin gray line that is also generated by ---.

A couple of days after that Chrome update, the update symbol showed on Brave too, so I updated it and nothing happened, the line was still rendered as if it were a ---.

Has anyone noticed this behaviour and found a solution? Maybe it’s because of some change in how the browser renders tags or something?

Note: I opened the same notebooks on JupyterLab, they are rendered fine there.

Thank you in advance!!

Source: Python-3x Questions