User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:84.0) Gecko/20100101 Firefox/84.0

Steps to reproduce:

I have a shortcut defined for some search, let's say "w" for Wikipedia Search. browser.urlbar.update2 is set to "true" as default.
Now I hit "w", <Space>, <Enter>

Actual results:

Hitting <Enter> does nothing.

Expected results:

In the past (I cannot tell exactly when it changed, though it was recent), and also in Firefox 84.0.2 with browser.urlbar.update2 set to "false", Firefox would submit an empty search. Then the current window would open whereever the website redirects empty searches. For example, for Wikipedia, that is https://en.wikipedia.org/wiki/Special:Search.

I used this feature a lot to quickly go to open some websites. Setting
browser.urlbar.update2 is a workaround for now. 1085374 is loosely related.

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

This change is expected, you should be able to autofill the search engine by typing the start of its domain anyway. See the various discussions and comments starting from bug 1675996 and its duplicates.