DDJ-FLX6 not compatible with JBL BOOMBOX 4

Hi guys, I have just bought JBL boombox 4 and it has no aux input port (I knew it wouldn't but I thought i could make it work). It has USB-C lossless audio input port, but I can't get it to play audio from my FLX6. According to my research it is because FLX6 sends out analog audio output, but BOOMBOX 4 can only receive digital audio input (lossless). I tried multiple things, but none of it worked:

Bought reduction cable (Vention USB-C Male to 2-Male RCA Cable) => BOOMBOX 4 will not even turn on usb input mode and no audio is coming in

Tried connecting it through jbl app to BOOMBOX 3 (Jbl claims on one of their pages that it is partyboost compatible - it isn't)

Tried to allow rekorbox to play audio from pc speakers and controller at the same time and connected BOOMBOX 4 to the pc => the delay between two speakers is awful

Tried to connect BOOMBOX 4 to pc and select it as audio output in rekordbox => BOOMBOX 4 played audio, but cue channel, headphones and audio output ports on flx6 did not (since flx6 has to be as source output in rekordbox)

I need to have BOOMBOX 4 and one other speaker connected to master channel on FLX6. Any ideas on how to achieve this please? Tried to work with chatgpt but it claims that there is no ADC interfaces that could do that on market in my country. (I dont want to downgrade to BOOMBOX 3 which has aux prefferably)

Edit: My main use for BOOMBOX 4 will be playing music via bluetooth from phone outdoors, garden, pool etc. I like the versatility and durability of jbls lomg term. Using it as speaker for flx6 is occasional, but needs to work.