Nice project! For anyone in this thread who'd rather not keep a Home Assistant add-on or any always-on device running, here's a different angle: STR (SoundTouch Reborn), an open-source tool I make.
Instead of bridging from a server, it sets the speaker up once via a USB stick (free Windows/Mac app) and then runs locally on the speaker itself. No Pi, no NAS, no HA instance, no networking knowledge needed. Internet radio and the hardware preset buttons 1–6 come back, fully local, no account or Bose server.
Not a replacement for a HA workflow if you're already deep in HA. Just a no-infrastructure option for people who want the buttons back and nothing to maintain. Disclosure: I'm the author, MIT license, not affiliated with Bose. https://st-reborn.de