I'd like to hear more about Odin + STM32 MCU firmware, do you have any good resources? I'm also curious how difficult it may be to using it with ESP32 (ESP-IDF) / RP2350.

You can look at my repo here: https://github.com/MadlyFX/odin-embedded-boilerplate

I don't believe Xtensa (ESP32) is supported yet, but people have been asking for it, so it may happen at some point. ARM is well supported now though, obviously.