Polish Keyboard on PC
I can't speak to a Mac user, but I use a PC and I can choose a Polish keyboard through the control panel. From there, click on "Clock, Language and Region". You would choose the "change keyboard" option. This brings you to a dialog box.
In the dialog box, you will need to "add" a keyboard. You can choose from hundreds of keyboard, but the choices are alphabetical by language. When you get to P for Polish, you should choose the keyboard for "Polish Programmers". Man, this keyboard is almost like the American keyboard. The layout is the same, unlike Spanish or French. All you need to do is press down on the "alt" key to the right of the space bar. If you press this alt key with the letter needing a diacritical mark, it will work effortlessly.
You can toggle between the English and Polish keyboard by using the shortcut, left hand side alt and shift.
I just toggled and now I can type the following diacriticals using right side alt:ą,ę,ó,ż,ć,ś. The incredible ź, different from ż, requires right alt with x.
If you have any questions, post them here. I hope that I have been a help.
I do Duolingo Polish on any of three platforms available to me. My I-Mac computer works best and has all the diacritic characters although the diacritical a is only available on the screen, not the keyboard. I like to use the Duolingo app on my I pad because of its mobility but it doesn’t have the diacritical a. My I phone is most interesting because it allows a Polish keyboard which enables Polish spell check. Don’t know why an app is missing a character.
On macOS go to Keyboard settings -> Input Sources -> click "+" on the bottom right and find "Polish - Pro" to get the same layout.
Btw, I recommend using programmers layout even if you're not a programmer, because it matches the US layout better and it's much easier to find letters with diacritics.
Use the RIGHT option (alt) key to access ą, ę, ó, ł, etc. Note that you can't use LEFT ctrl + LEFT alt for this, unlike on Windows.
For myself, I use the program AX.EXE, available from http://vulpeculox.net/ax/
This is PC Windows only, and some virus checkers/other security systems object violently. I find it invaluable for German, Polish, Hungarian, et al.....
EDIT: March 26th, 2020. I am now 'resting' my Duo Hungarian lessons as the conference I had been planning to attend has now, of course, been cancelled :-( .
Well, Amazon.co.uk has a couple for a start.....
Disclaimer: I cannot vouch for the accuracy of these vendors' descriptions, or for the reliability of these vendors.
Oh, and I don't work for either of the vendors or for Amazon.
Try the Polish (214) layout. I don't know anybody who actually uses it in Poland, but it seems to be the perfect fit for you, as it's a QWERTZ with Polish letters on separate keys.