This is a known problem. I'm happy to provide you with a BLOG entry on this: https://www.spickipedia.com/index.php/samsung/samsung-das-angeschlossene-usb-geraet-wird-nicht-unterstuetzt.html, the adapter mentioned is this one: Samsung USB-C Audio Adapter (USB C, 3.5mm)

It works well on an old car radio from 2009 with a 15pro max on the aux input.

According to the specifications, the cable is designed to connect a source (e.g. a mobile phone) with a Type-C output to a playback device with a 3.5 mm jack connection. What you want would be the opposite, so to speak, which is why I can't guarantee that this will work the way you want it to.

According to my research, the USB-C Port of the JBL Flip 5 is only for charging and is not able to carry an audio signal. If your Samsung TV supports Bluetooth, you can try to connect your Flip 5 wirelessly (This will introduce a slight delay with the picture though).