today I searched Internet on how to transfer a file from Android, succeeded to send a photo to my UT phone using Bluetooth, it works.
Notification is less clear than with Android, there is only a sound, no visual prompt, and it's necessary to open the application, see the prompt in the app, download the file to a folder, then it's finally possible to display it. On the whole the receiving file UX is behind what Android (14 in this case) does and not as simple as transmitting files from UT toward another device.
While doing some stuff on the Android phone, I noticed that there was some sound on the UT phone, like if the 'keys' entered on the Android unlock screen had a sound echo on the other phone. Looking at it a bit more, playing a sound on the Android phone is done on the UT phone. If one don't want to turn the UT phone into a speaker, it's a bit disturbing. It's not a problem with the app itself it seems, as when pairing under UT there is no idea of well, rights, it's all or nothing. To compound the problem, the UT phone is turned into a speaker to the point that the hardware controls on the phone have no effect on the sound level - it's entirely controlled from the Android phone.
Edit: I tried to play a sound on the UT phone and it played on the UT phone, not the Android. So clearly it's technically possible to accept files without being a speaker, however it does not seem possible on Ubuntu Touch. A quick search of the issues does not bring anything related so either I'm mistaken or no one sees this as a problem.