A good rule of thumb is that if your phone has a headphone jack, it also has FM radio. And whether it has a headphone jack depends on whether the phone aims to be waterproof.
Waterproof phone = no headphone jack = no FM radio. There are some exceptions, but it's more often true than not.
Every Samsung galaxy flagship from the S4 to the S10 had a headphone jack and was waterproof. This heuristic only works for recent models where headphone jack means it's a budget model and they've probably skimped on waterproofing.
the USB connector is a box that is not open to the inside of the phone, at least every one i've seen. I've even seen a couple of phones where the box that held the USB connector also had a speaker in it. I guess a headphone jack could be put inside of a similar box, but the main difference is all the contacts in TRR plugs are spring metal that are attached to the outside of the plastic housing and poke through, and that's if the spec calls for any sort of reinforcement. The simplest headphone jacks are just spring metal in empty space.
radio in englisch is quite overloaded, what do you mean? an fm receiver? a shortwave transceiver (as is the case in the 10m band)? a vhf/uhf transceiver to participate in lpd/pmr/fmrs, 2m/70cm ham?
My bet is countries having all kind of taxes, stamp fees etc when it comes to adding such features and phone makers not wanting to pay the fee. Or maybe it is a patent fee. Your device can support FM or can play radio? You need to pay 20 cents per device!
No, it's just that apple disabled it first and many others blindly followed. My samsung s10 still has FM radio (and phone jack). It's also energy efficient
Many phones had FM, but if you look the models for Verizon had FM disabled. The international versions had FM, AT&T had FM, Verizon didn't. They are also much more likely to lock their bootloader, and other anti-consumer things.
The older Freestyle (IIRC) also had this. It was my first "smartphone" before I got a real smartphone. I actually kind of miss being able to listen to the radio that way. Not sure how well it'd work these days since most people use wireless headphones.
They are implemented in the existing chips just not enabled in software. Qualcomm's ubiquitous LTE modem chip has FM radio baked in. There was a whole push by the FCC in the US as well as some FM broadcasters to mandate it be enabled. See:
"Your Phone Has An FM Chip. So Why can't you listen to the radio?":
it's a kneefall to Spotify/apple music/youtube music
That seems unlikely, radio (even Satellite radio) is not the same product as streaming music. My car has an AM/FM radio, the only thing I've ever used it for is tuning in to roadside traffic alerts when the sign is lit. The car came with 6 months of XM/Sirius satellite radio -- I tried out the Satellite Radio on a long road trip but didn't last a day before I went back to Spotify where I have full control over the music that's playing and can skip and rewind songs at will.
I don't think streaming music has anything to fear from FM radio on phones, I think the reason phones don't still offer it as a feature is because no one wants it.
I know about an Italian law from 2017 mandating that "all devices with FM radio must also receive Dab + services" [1]. Phones with only a FM chip obviously don't receive digital radio so I remember that as unintended (?) consequence Samsung was releasing updates to disable the chip. However the FM radio in my A40 still works.