Physical keyboard layout menu not showing when keyboard connected to iPhone / iPad (iOS 13/14)
With the keyboard connected, go to Settings → General → Keyboard → Hardware Keyboard.  Then tap over at the right edge and you will get a list of layouts to select.  Do not select &quot;Automatic&quot;, but the one you want to use.  I think you should be able to choose among at least &quot;Polish, Polish Pro, and ABC Extended&quot;.
If a layout you want to use is not on the list, there is no way to fix that, as Apple has not yet provided a means to add custom hardware layouts in iOS.  But you can ask them of course, via their feedback.
If you do not see the Hardware Keyboard setting when the keyboard is connected, then there is some kind of compatibility problem.  I have not heard of this happening with other Bluetooth keyboards up to now.