SixBack — Web Flasher

Plug your ESP32 board into USB, then:

Pick the serial port, and the flasher installs SixBack … — the right image for your chip is chosen automatically. Afterwards it asks for your WiFi, then SixBack finds and migrates your speakers on its own. Presets survive.

Already running SixBack? Update from the stick's own page — ⚙ SYSTEM → Update — no USB needed.
Special boards (8 MB S3, 16 MB C5), board identification and manual flashing: boards page.