I went looking in the play store yesterday for a Klingon keyboard. Something with all of the letters already capitalized, or not, as needed, with the combo letters already together and the such. I didn't have any luck. Does anyone know of such a keyboard?
I'm not sure about the IOS app, but my Android app (Anysoft) will still output the Latin characters that Duolingo expects, even when pIqaD keyboard is selected. So I can do some of the Duolingo lessons in pIqaD (this would not apply if your keyboard output the Unicode codes for the privately-defined area where some pIqaD characters are mapped).
I'm not sure about Win10, but for Android, if you download the AnySoftKeyboard and then add the quja' extension (both available in the Play Store), you can get a keyboard which already has the letters in the correct capitalization and the multigraphs on single keys. It also includes some options for pIqaD.
You seem to have figured it out, but in case someone else comes to this forum and wonders... pIqaD is the Klingon characters that are used to write Klingon instead of the Roman letters that Duolingo and most of the instructional materials use. quja' is the name of the Keyboard layout used when the quja' extension for AnySoftKeyboard is used, it has no other meaning in tlhIngan Hol that we know of. You can find it by searching for quja' in the play store, but it won't do anything unless you have AnySoftKeyboard installed and restart your device.
I like the arrangement of the quja' keyboard, makes typing suffixes like 'a' and 'e' so much quicker and easier, and then typing words like torgh is easy as those keys are more or less adjacent and a quick clockwise motion types it out. And of course ng, ch, etc. are one letter and one can't type an "n" then a "g" to get the former. tlhIngan is only four letters. Etc. The only thing I'd want to adjust is the red color of the roman covers, which is very low contrast; I'd go with yellow or white. The "regular" quja' keyboard has good contrast, but as AaronTurne noted, the I and the l basically look the same. Can one customize the color? Also after typing on the roman quja' for awhile I decided to try the pIqad keyboard and was able to manage because the quja' makes one think in terms of the Klingon letters, not English representations. :)