I got Razer Kishi Ultra one week ago, and found that the 3.5mm audio output has a weird issue which will output noisy electronic sound after long time (>20 minutes) of use. With the supports from the staff in Razer store, I tried 3 different units, different wired headphones, and the issue still occurred. I haven't test different phones, but since my other cheap USB-C controller, also with a 3.5mm audio output, doesn't have such issue, so I doubt it is caused by my phone.
If you wonder how bad the audio could be when this issue happened, you can check this one minutes long video, which the first 30 seconds shows the normal audio output, and the rest 30 seconds shows the abnormal audio output (better turned down the audio volume cause its really uncomfortable to hear).
Hope the employees from Razer notice this issue and start to investigate it. I have returned my Razer Kishi Ultra cause right now it's not working properly for me, but if one day Razer fixed this issue with new hardware or firmware update, I will be glad to purchase it again.