You can essential use most intern webpage searches as search engine (Wikipedia, Forums, Tech pages, Newspaper, etc.), so you can find always what you need, general or specific information.

To insert a page search in your search engine list, mostly it's enough to search something in this page, after this editing the URL in the adressbar substituing the search concept with %s (eg. https ://lemmy.ml/search?q=%s) and copy than the URL in your search engine list. In Vivaldi it works also with the right click on the search bar and select "add as search engine" from the context menu.

In the Vivaldi forum there is a threat with the IMHO most extensive list of search engines with corresponding insert codes.

https://forum.vivaldi.net/topic/46609/guide-vivaldi-search-engines-collection