I found out what's the bug/issue here.
If you install quickstart for J5 everything is ok with fonts, but when change something in /layouts/default.php fonts will change to the same issue i'm having.
For a quick test you can go to default.php and in the end just add one more line, click save and your fonts should have the same issue as mine.
Originally i had to go to default.php file to change this:
<div class="gkSocial" id="gkSocial">
<span class="fa fa-share-alt"></span>
<div class="gkSocialWrap">
<a href="#" class="menu-social facebook" title="Facebook"><i class="fab fa-facebook-f"></i></a>
<a href="#" class="menu-social twitter" title="Twitter"><i class="fab fa-twitter"></i></a>
<a href="#" class="menu-social instagram" title="Instagram"><i class="fab fa-instagram"></i></a>
</div>
</div>
And it was after that that i had the issue with fonts.
Even if i change for the original default.php file, fonts still have the same issue/bug, it seems that happens after any editing/change on default.php and after that there's no coming back.
Is there anyway to fix this? I can install quicksart package, redo everything and not edit nothing on default.php but i'll have to change gkSocial and i don't see any other "place" to do it.