Sorry, what's a "SPA" - can't seem to find it by Googling.
firefox "https://en.wikipedia.org/w/index.php?limit=500&profile=all&search=spa"
https://en.wikipedia.org/wiki/Spa_(disambiguation)
A more specific search, e.g., "single page", will not redirect.
In some ways, for discovery, Wikipedia's search engine is better than Google's. For one, it is non-commercial and does serve ads based on past surveillance of the user's activity. Second, the user can retrieve larger numbers of results and page through them quickly without triggering a (false positive?) defensive measure than temporarily blocks her IP address from retrieving results for a defined period. Third, it is curated to remove commercial content rather than curated to further a business purpose in online advertising.
No wonder Google steals Wikipedia content for "instant answers" or whatever they call it. Wikipedia search works quite well.
https://en.wikipedia.org/wiki/Spa_(disambiguation)
In that sense Wikipedia is a bit like Google in that they try to guess what the user is searching for, perhaps what is most popular. Thus, a search for "SPA" automatically redirects to the article on Spa as in therapeutic water treatment. A link to the Disambiguation page, if it exists, will always be provided (cf. "Did you mean ....").
However, change the search string "spa" to something more specific and then see all the search results.
For example:
https://en.wikipedia.org/w/index.php?limit=500&profile=all&s...
Increase limit= to a number greater 500 if desired, or smaller if want to speed up the search.