You need to download "Samurai Focus Fix" and enable it in AML. Go to its folder (steamapps>workshop>content>268500>2933758179) once you're there, go to Config>XComGame.ini and below "+PerksToGrantFocusKillTracking=Shinigami" write this line:
+PerksToGrantFocusKillTracking=TemplarFocus

That's it, you can now gain focus.

This wouldn't have been possible without RustyDios, not only for creating Samurai Focus Fix but for providing this fix itself when I asked him about this issue.