Can you link what you are referring to?
Here and here and here, as well as the fact that threads such as the recommendations have to exist here which do contain comments going beyond the integrated DAC issue. I have previously asked the question elsewhere and users have said they have the same issue.
Can you define what “known” means?
I know they are in working order. They are “known good”. Both of them work for audio connections with other devices.
Have you had a look here?
I have now. One of them is the Belkin adaptor listed there. The other one is made by “jsaux” which has previously worked with the FP4 yes.
You have edited my post title incorrectly, please don’t do that, and please change it back.