User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:83.0) Gecko/20100101 Firefox/83.0

Steps to reproduce:

When I use a search shortcut in the address bar without passing any arguments, Firefox open the first link in the history, example:
I've the search engine "YouTube" with the keyword "yt", where if I use something like "yt Michael Jackson" it's works but if I use only "yt" it doen't work anymore.

Actual results:

When I type the keyword of a search shortcut in the address bar Firefox open the first link in the history (without treating the string as a searh shortcut).

This happen with all search shortcut.

Expected results:

When I type the keyword of a search shortcut in the address bar (like "yt"), Firefox should treat it as a search shortcut and open the corresponding search engine link (like www.youtube.com).

Note: before Firefox 83 (82 and earlier) this was the normal behavior.

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

This is the expected behavior, we don't think going to the search form is particularly useful when the same search can be executed from the urlbar itself. For now you can use bookmark keywords, or just click a bookmark or type the first part of the domain and use autofill.

I understand that you think this behavior it should be the best and for now I'll follow your suggestion but Firefox unlike other browsers should be highly customizable not only for the look but also for the behavior, so I suggest to add an option for this, if going or not to the search engine home, maybe in about:config if you think it's superfluous.
I hope you hear my suggestion, it's only for Firefox's sake.
Thank you.