How to use a custom search engine

Google Chrome, Vivaldi, Opera, etc...

If you plan on using only Google, the flag enable-windows-desktop-search-redirection is your friend.

If not, the Chrometana addon works for you.

Firefox, Waterfox, Palemoon, etc...

Under your search preferences, check the box labelled "Use this search engine for searches from Windows"

Internet Explorer, Edge and other browsers

You can use @FelixSe's fork, available here.