Solution 1:

Until we find a solution, I am trying to change language quickly (not press the buttons for too long).

If I am pressing Alt first, I am releashing it quickly after pressing Shift.

If I am pressing Shift first, it doesn't matter how long I keep the buttons pressed - the popup doesn't appear at all.

I hope this helps..!

Solution 2:

I used Windows 10 Tweaker (Google it. It's free and you can upgrade to premium if you wish but free does the job well too).

Select "Preconigure Explorer", then click on "choose" and select "Remove language pop-up..." then click on "Apply".

p.s. Antivirus apps get crazy so don't forget to disable them before downloading and then archive (just in case the antivirus deletes it after the job is done because you might need it). Another thing I encountered was that whenever I hover the mouse over the "Apply" button, tweaker gets closed by itself. I then basically used "Tab" or/and "Shift + Tab" for going forward and backwards and "Space" for selecting and "Enter" for applying. Be careful with the other functions of the tweaker as you might brick your Windows.

EDIT: This worked on Windows 11 Pre-release but doesn't work on the released version of Windows 11.