User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:69.0) Gecko/20100101 Firefox/69.0

Steps to reproduce:

I updated Firefox to version 69.0 (Firefox in Ubuntu, x64). Then I tried to navigate to some sites using the URL autocomplete from the browse history.

Actual results:

When I type specific domains to the location bar, the pages don't get automatically completed. I do get search results for these, but they don't get autocompleted. This has lead me to search "you" multiple times, for example, when trying to go to youtube.com, etc.

Expected results:

The autocomplete should have filled for example "you" with "tube.com" and navigate to youtube.com when pressing enter.

I'm fairly sure that this has something to do with the Firefox database, as when I create a new profile and try the same sites, they work fine. I did not find any common factor with the sites for which this is failing (with/without "www." prefix, http/https, a page on the domain has/has not been bookmarked, ...). A list of sites that are failing for example are:

www.youtube.com
www.facebook.com
www.iltasanomat.fi
www.riemurasia.net
www.mbnet.fi

I have experienced this on at least two different OS installs (one on Windows, one in Linux). But when I create a new profile, the problem doesn't seem to exist there, so I believe there has been some incompatibility with some database introduced in the update, or the update has caused some corruption in migration to a newer version. I tried to clear the history related to one of the domains (history -> search by domain -> right-click and "Forget this domain"); however, that did not help, so a more thorough clean is required.

did you disable bookmarks in the urlbar preferences in about:preferences#privacy?

If so, this is a dupe of bug 1582234

That is true, and the issue seems closely related. I have some additional findings that I will report in bug 1582234. I'm not sure if I'm allowed to mark this as duplicate myself, but please feel free to do so.