I believe it is T-Mobile and Starlink, though very early stage (just a press release[0] about "a vision to give customers a crucial additional layer of connectivity" that "aims to work" with existing phones, far as I can tell).
And yes, the Apple announcement is just the productization of a feature in the Qualcomm X65[1]. But I think this is a case where the technical implementation is the easiest part; I would be surprised of other X65 adopters also delivered satellite comms, at least unless/until it's obvious it's driving phone purchasing decisions.
"Band n53" has been widely reported in the context of various iPhone satellite rumors, but I still believe that this was actually just bad reporting: Band n53 is essentially terrestrial LTE/5G usage of Globalstar's global spectrum rights in a band that was previously designated for ground-to-space usage.
Whatever the iPhone 14 is using to talk to the Globalstar satellites, I'd be extremely surprised if it looked anything like LTE or 5G at the physical or logical layer.
I remember reading that they are in fact using n53 2.4Ghz. Remember this is a fallback for areas without cell service, and a satellite signal is much weaker on the ground than any terrestrial signal.
Given that it's a two-way service, and Globalstar satellites use the 2480-2500 MHz range for downlink transmissions, it must be using 2.4 GHz, yes.
But my point is that this probably has very little to do with Globalstar's terrestrial band 53 efforts, other than possibly sharing some HF hardware in the new iPhones given that they support both that terrestrial LTE/5G band and satellite messaging.
I think it depends massively on how much it costs the company to provide. If it's just a chip and a bit more software I think companies will include it. It's not clear from the press reports if the money Apple spent on building up base stations for this are just for them or if the satellite providers could use them for other companies phones.
And yes, the Apple announcement is just the productization of a feature in the Qualcomm X65[1]. But I think this is a case where the technical implementation is the easiest part; I would be surprised of other X65 adopters also delivered satellite comms, at least unless/until it's obvious it's driving phone purchasing decisions.
[0] https://www.t-mobile.com/news/un-carrier/t-mobile-takes-cove...
[1] https://9to5mac.com/2022/09/18/iphone-14-satellite-connectiv...