openAV-Ctlra VS mixxx

I have been talking to the author of Ctlra who has reverse engineered the screens. The screens work by sending a bunch of pixels to a vendor defined class USB bulk endpoint. Unlike some other controllers with screens which just take some metadata from the software and do their own rendering, Native Instruments controllers with screen rely on the software to do the rendering. Traktor does this by rendering QML to an offscreen buffer. However, according to the author of Ctlra it is more complicated than that to get 60 FPS framerate to the screens because simply sending all the pixels continuously saturates the USB bus. Fortunately that doesn't interfere with any other features of the controller because the other USB signals have higher priority (isochronous for the audio, interrupt for the HID). So to get a good framerate, which would matter for sending scrolling waveforms to the screens, my understanding is that Mixxx would have to compare every rendered frame to identify which rectangles of the screen to update in each USB packet.

Mixxx is excellent and has pretty wide hardware support.

FYI the "limited" functionality of Rekordbox can be hardware unlocked with some Pioneer controllers.

https://mixxx.org/

There are quite a few DJs that use Ableton for DJing (or hybrid sets). Of course, Ableton wasn't made with DJing as its main function in mind but you totally can use it for that purpose and (with some tweaking) do everything and more that would be possible in a dedicated DJing software (like Traktor or Rekordbox or Mixxx)

I’ve used Mixxx a little bit and have been surprised how capable it is. It’s an open source project and is free to download: https://mixxx.org/

Mixxx (this one's free)

Mixxx

Related works: https://github.com/mixxxdj/mixxx/pull/4027

Mixxx (you already mentioned this; it's certainly a great piece of free software to test the DJ waters with and works with a lot of gear).

Alternatively, you can also use Mixxx with the S4 MK2. Mixxx is free. But instead of a Traktor control vinyl record, you'd use Serato timecode instead, as stated in the docs.

If the device is class-compliant, i.e. it follows the generic USB spec and doesn’t need drivers installed, it can work under Linux. However the free software you get with the controller (Serato, Rekordbox, Traktor etc.) won’t. The alternative is to use Mixxx. It’s free and open source. You can check their controller support. https://mixxx.org/

If you don't like any of those, aren't you glad you didn't spend the money to find out the hard way? There's more DJ software than those two, so try out these as well: Traktor Pro 3, Virtual DJ, DJUCED, or Mixxx.