In theory you can use those AptX Adaptive USB transmitter dongles to output AptX Adaptive with any device that has USB. So use USB-C or USB-A adapters/converters if needed. Or in your case probably a Lightning converter/adapter.

Btw, it seems you have to get the 16-bit version for compatibility with older devices like say TV, otherwise go for the 24-bit version as those are often newer and have bugfixes and so on. They're like the same price, so just get the 24-bit versions of the AptX Adaptive dongles.

There's a Lightning/Apple version for the AptX Adaptive dongle (KB8(P)), it might be on one of the AliExpress listings still, but it'll be on Taobao for sure.

So just to be clear, if you get the $15-20 KB8P or KB9P dongle for your iPhone (or really any device that can output sound with USB, in theory), then it should output AptX Adaptive. So your TWS earbuds, Qudelix 5K, et cetera should get AptX Adaptive too.

If you don't have that KB9P/etc. dongle then it'll likely just be AAC with the Qudelix 5K and your TWS earbuds. As yes unfortunately iPhones/Apple devices pretty much just have AAC (and SBC), and so you'll need those extra transmitters to get the other codecs like AptX Adaptive and LDAC.

With Apple TWS earbuds or Bluetooth devices, those have hardware/software/etc. onboard that make them sound good (through AAC) when paired with iPhones or other Apple devices that have a particular chip, like the new H2 chip or something like that.

But ya with Bluetooth amp/DAC dongles like the Qudelix 5k and basically other non-Apple TWS earbuds and so on, it'll just be AAC only.

The main selling point of the overpriced ($130) FiiO BTA30 Pro is probably the LDAC through USB. But it's not like a dongle, it's not really portable with the phone.

A bunch of us are actually in contact with the Taobao/Chinese sellers or manufacturers that are making these AptX Adaptive USB transmitter dongles. You can use the Taobao shipping agents like Superbuy/ParcelUp/CSSBuy/et cetera to navigate the Taobao site with English translation, and when you actually message them through Aliwangwang or the messaging system, they have decent English due to the autotranslate and so on system.

Anyway, maybe earlier this 2022 those Taobao sellers said that the new Bluetooth 5.3/etc. dongles with LDAC and so on are in development, but sadly ya they're still delayed. For reference, they released the new KB8P and KB9(P) around January to April 2022, I forgot now.

So for now no LDAC USB transmitter dongles, same with the AptX Lossless USB transmitter dongles, though it seems there's some other companies (like say Nura with their NuraTrue Pro TWS earbuds) that are trying to get those AptX Lossless USB transmitter dongles out soon too.

TL;DR: get KB9P dongle as it will give your iPhone AptX Adaptive and so on.