Text section is not on focus when jumping to a page (up/down arrow keys)

For the web page to accept arrow keys or page up/down for scrolling, I have to be in your text panel first.

Is there a way to get the text panel in focus by default when opening a link

Try here, using the up/down arrow keys without using the mouse (then use the mouse to focus and try again).
https://correaa.gitlab.io/boost-multi/multi/reference.html

Start with the linked reference page and reproduce the behavior using only the up/down arrow and page-up/page-down keys before clicking the text panel. Trace how the page opens and assigns focus to the text panel; done means those keys scroll the text immediately after opening the link without mouse interaction.

Written by the indexing model from the issue text.