Icons showing as squre
Same problem here in a fresh install, it seems everything is correct but font-awesome icons show as squares.
--Edit: Solve -> Install npm dependencies in the folder of Theme AdminLTE with "npm install" and "npm run dev". Font-awesome compile perfect and show the icons
@cesar magic solution
This is almost for sure git changing your line endings in the font files (.woff and so on) and will likely break again when you do another push/pull in git. Your browser will keep good ones cached so you may not see broken ones if you have pushed, but new users will likely see the broken icons.
Because these are binary files, when git changes the line endings it breaks the fonts.
You will have to get a good copy of the fonts again then add this to your .gitattributes file
This tells git that the files are binary and it won't try to change the line endings anymore.