Update:
I bought a Samsung S9, which has the necessary hardware for usb input, and tested my Scarlet Solo using a usb hub. The Scarlet Solo works natively with Linux, in my experience.
When running on /e/ OS, the audio interface worked perfectly. The S9 recognised it as a sound card and audio came through it. I plugged my bass in, which all functioned perfectly as well. I downloaded n-Track Studio DAW for free through the /e/ App store and recorded some bass, as well as putting a drum loop to it. Latency wasn't a problem, though playback always started with a horrible sound. Still, relatively speaking, all good.
I then flashed UT to the S9. On UT, the phone recognised the interface as a storage device and no audio came through it, playing through the speakers instead.
So, @animaldaydream, since it works on Android, perhaps there is hope for UT? It doesn't recognise all usb devices as storage, my keyboard and mouse function as expected.