Which line did I suggest you add to .xsession? In which post did I make that suggestion?
He must be referring to my suggestion in
If you are using Xorg you can just add...
Which is strange that it didn't work. Assuming you correctly placed this line at the end of the .xsession and it still didn't work, I can only conclude that you are not using Xorg.
Also, initially, i didn't know that you were referring to PiCore, because I don't understand anything about PiCore and I don't even know if it works the same. You should have said it was picore or created the topic in the picore session.
Keep in mind that there are some extensions that reset the keyboard defined by setxkbmap, for example raid-dm (this only happens when the extension is loaded manually, after login)
Could you share the contents of your .xsession and, with Rich's help, be sure you're using Xorg?