You've got to hand it to the 'hacker' community, in this case Phorepoc (based in Greece), who has tweaked the DarkStream 2.2 Nokia N97 classic firmware that I'd previously played with but ultimately rejected because Qt and SmartInstaller wouldn't run on it, meaning that a vast swathe of modern applications were ruled out. Phorepoc has Qt 'fooled' into running perfectly and I report below on some of my findings with this new firmware.

From his blog post:

The fix is nothing more than a dirty quick fix to IaguCool IC@Darkstream CFW for N97 Classic that will let Smart Installer bundled Qt applications to properly install. Those are actually all the Qt applications you can find on Nokia's Store. The fix was first implemented on my own beta version of Phorepoc CFW (version 1.99) and does nothing more than tricking the system into thinking that some libraries are installed in C (and so kill the dependency checks when installing qt apps). It was the only solution I could find back then as the system couldn't recognize the files integrated into the firmware.

It took me a few hours to re-implement it to IaguCool's CFW as it's been almost a year since the last time I modded a firmware but it's finally here. Nothing else has been changed on the firmware as I wanted to keep it clean and simple with no extra baggage. Download links are provided below along with the needed installation packages for qt and python, modified to install in E for saving valuable space on phone memory.

IC@Darkstream version 2.2 with Qt Fix 
Qt and Python files

PS: I hope I wasn't late enough for that fix, although Google's latest changes regarding Mail for Exchange support is an overkill and you'll have to think twice before going that route (a hard reset is essential for the qt fix to work). 

Great work, I installed this firmware using the usual technique, and found that, indeed, Smart Installer now worked fine and that in addition to the other benefits of the Darkstream firmware (including a working FM transmitter, a fairly up to date version of Nokia Maps/Navigation and the editing version of Quickoffice 6.2), I could now install Qt-based applications to my heart's content.

With the supplied Qt binaries installed (choosing disk E: wherever possible), with the Nokia Store fully updated and with all my core applications in place, I still had 56MB free on the system disk (C:), which is impressive.

There are a few things to highlight about the procedure:

1. The download links above lead to Mediafire - I suggest you go there with your antivirus system activated and your common sense well and truly engaged - be wary of 'fake' adverts that try to encourage you to click them!
2. The phone will be hard reset/wiped, so back up anything you might have on the system disk and want back, in terms of documents and media.
3. After installation, wait a minute or so, for the specific Phorepoc scripts to run, patching the OS for Qt.
4. Before installing the supplied Qt binaries, you'll need to go into Tools | ROMPatcher and turn on 'Install Server'.
5. Ignore all suggestions in 'Sw Update' about updates waiting - you probably don't need any of these - they're either included/patched already, or are a bad idea in terms of eating up disk C: - remember that Sw Update doesn't know you've got a custom firmware, so it's making some bad assumptions about what you might need or want.

The new 4-wide app grid in the DarkStream firmware; (right) enabling Install Server, so that the modified Qt binaries can be installed

Moment of truth time - installing a Qt application - all worked fine!

Comments welcome if you have a crack at all this on your own N97 classic, which has otherwise probably been gathering dust in the corner of your desk! Maybe all is not lost for this venerable device after all?

PS. The usual disclaimers apply - we take no responsibility for any devices bricked through this sort of misadventure!