It is interesting that they have a day devoted to embedded using MicroBit v2.
The older Rust-Embedded Discovery book [0] also used Microbit but the later edition [1] suggests a STM32F3DISCOVERY. For RISC-V and Extensa fans there is also Ferrous Systems' Embedded Rust on Espressif training material [2] which has a coordinated board [3] that has been "cloned" by Wokwi [4].
0. https://docs.rust-embedded.org/discovery/microbit/index.html
1. https://docs.rust-embedded.org/book/index.html
2. https://esp-rs.github.io/espressif-trainings/