Search functionality not working in locally installed user assistance

From this document,https://help.3ds.com/2020x/English/DSDoc/FrontmatterMap/DSDocHome.htm?contextscope=onpremise

It's mentioned Internet Explorer 11 is mandatory to use search functionality in locally installed user assistance document.

Internet Explorer is officially retired. Why search is not working in Firefox or any modern browsers?
How to fix this?

TIA