Hi, I ask myself if the person, who wrote this article ever tried this setup. Comparing the audio jack from a pi with a sonos is just a joke. Of course there is a possibility to use the pi for this, but not with its audio jack.
the raspberry pi audio jack is a pwm driven output, no real DAC behind it. It sounds simply AWFUL. There is nothing else to say, look at measurements. If someone does not hear this, go to a doctor. The sound is smeared and sounds very harsh and digital.
Buying an inexpensive DAC board for the pi is the way to go if you want to compare it to the sonos for example. There are PCM5122 based sound boards for about 20$ and this increases the pi sound quality VERY much.
Using the 3,5 jack and talking about sound is like driving a 40 years old fiat panda and comparing it to a new ferrari. At least both have 4 wheels, i know.
Please investigate first, before writing such nonsense. There are people who read this here and get very disappointed by the sound if they try this setup.
Sound quality is often determined by total harmonic distortion. A sonos you want to compare with has a THD of about 0,03% at 10kHz. A raspberry Pi DAC board about 0,08% at 10kHz. The audio jack has a THD of 10% at 10kHz. This is garbage, not sound. Also the high frequencies are not reproduced at all. The normal hearable audio range depending on your age is between 20hz and 20.000hz. All DAC boards and the sonos reproduce this range. The pi audio jack stops at 15.000hz, because of the high pass filter and PWM limitations.
Even with a DAC board the raspberry pi4 is a bad choice for audio reproduction. Its high frequency CPU induces so much electro magnetical interference, that you either need to underclock it a bit or at best take the raspberry pi3b. Its EMI numbers are much better and do not disturb the amplifiers speakers so much. Faster is not always better. The Pi3b has all the features needed here too, like Wifi and BT.
Please write articles about somethink you know about, this is just waste of webspace, sorry. Its also misleading people by comparing it to entry level hifi systems like the sonos. People reading this here, who buy a pi4 for this purpose are just wasting money and should know, that at least a DAC board is needed to make this here work. Even then you are not at sonos level of quality and by far not in hifi territory, but this wasnt intended, i know.
Please write this into your article or delete it, dont mislead people with bad investigated knowledge.