there are plenty of discussions about it. I didn’t find full solution. You can add google as a search engine. But suggestions don’t work for me.

My approximate solution

1. remove standard firefox:

    sudo apt-get remove firefox
   

2. remove search addons. Source. I am not sure if this step actually helped. TODO: Check if it is required.

    sudo apt-get remove mint-search-addon
   

3. delete file (or rename to have a backup):

    ~/.mozilla/firefox/<SOMETHING>.default/search.json.mozlz4
   

   and contents of the directory:

    ~/.mozilla/firefox/sf8ha7dx.default/searchplugins
   

4. download, install and run firefox from official website. It will create a new version of

    ~/.mozilla/firefox/sf8ha7dx.default/searchplugins
   

5. in .mozilla/firefox/sf8ha7dx.default/searchplugins create a file google1.xml with contents:

    <SearchPlugin xmlns="http://www.mozilla.org/2006/browser/search/">
    <ShortName>Google1</ShortName>
    <Description>Google1</Description>
    <InputEncoding>UTF-8</InputEncoding>
    <SearchForm>http://www.google.com</SearchForm>
    <Url type="application/x-suggestions+json" method="GET" template="http://www.google.com/complete/search?client=firefox&amp;q={searchTerms}" />
    <Url type="text/html" method="GET" template="http://www.google.com/search?q={searchTerms}" resultDomain="google.com">
    </Url>
    </SearchPlugin>
   

6. remove official normal version of firefox

7. install mint version of firefox:

    sudo apt-get install firefox
   

   Now “mint” firefox will use search.json.mozlz4 version from normal firefox and suggestions should work

8. Optional. I also removed (actually renamed) from /usr/* all directories like searchplugins that contain files like yahoo.xml. I think they are created by “mint” firefox. Not sure that it is a necessary step. Further check is required here.