You could try routing your sound through a computer. Just use the rca master out on the RX. Make sure you raise the level on the audio input channel. If you have your computer connected to a couple of decent speakers it should do the trick. Now you can send the incoming sound to where you want it. I’ve used a setup like this in more than 15 years and it has always worked perfectly. I have an older dedicated computer for this still running Win XP and the programs I use for capturing the sound is as old. If it works, don’t fix it 😉 . I’ve also tested this solution with my laptop running Win 10/Audacity. It’s important that your sound card have a line in connection. The ”mic in” will not give you a good sound quality and is not an option. In some laptops Line in/Mic in is shared and then you have to do the settings in the software provided for the sound card.
If you’re also gonna use a mic, rec out on the mixer is not an option anyway, as it will only send what comes from the channels. Using master out will send everything you can hear in your speakers. If you have active monitors, connect them as usual to the XLR out. In my case I have a YAMAHA stereo amplifier as a audio hub where I connect my computers to. My DJM-900NXS2 is connected via the Rca Master Out to my recording computer, that is connected to the YAMAHA. I have other mixers, analogue ones, I use too, so I see no point in using any other solution for recording audio. It’s perfectly fine to mix to the sound that comes from your computer if you don’t have active monitors connected to your RX. Nothing to worry about.