With the squeezelite-esp32 software, you can

• Stream from LMS and send audio to the build-in amplifier, the line-out jack, the spdif connector or another Bluetooth speaker. You can also use an external I2S DAC if you connect it to the general purpose 5/8 pins connector and tweak the software. Synchronization works.
• Stream from a Bluetooth device and send audio to the same outputs, except of course for sending to another Bluetooth speaker … There is no guarantee of audio/video synchronization at this point
• Stream from an AirPlay1 device (iPhone, iTunes …) to the same outputs, including to a Bluetooth speaker. Synchronization works.
• Add your own buttons, rotary encoder and map/combine them to various functions (play, pause, volume, next …
• Use IR control by adding a simple receiver compatible with 38kHz device (no pullup resistor or capacitor needed)
• Add a display like this one which can be directly connected to the 6-pins header. Currently SH1106, SSD1306, SSD1322, SSD1326/7, SSD1351, ST7735 and ST7789 displays are supported.

github.com/philippe44/SqueezeAMP