It’s frustrating though to see Sitejet is still recommending a +2-year old solution that doesn’t work anymore. Please see my below screenshot that does not look like the one in the guide linked above. I’d like to know where to find this search widget; it’s not even listed on Elfsight’s own website.
That is indeed frustrating. Another case where we can all thank Google for being “the good guys”:
Eh, I’m sincerely not actually trying to blame anyone for the no search. If Sitejet’s team can’t do it, they can’t do it, and I just have to live with no search. That’s life sometimes; que sera, sera 
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I meant more so how my quest to add a search feature pointed to Sitejet’s own help section, which still (even today) says that Elfsight’s search widget is still offered as before, when my screenshot demonstrates that to be incorrect. I believe nobody gets to blame that on Google.
I do understand. Well, in this case we can actually blame Google for that, as they stopped the access. 
We have not received any notification about that.
I have put an update for the help section on the list about this article. Thank you for pointing out the change!
Hopefully, we will be able to find a native solution soon for all of you. 