Ask HN: What Open Source Embedded C++ should I read?

My side project for an embedded esp32 device has become quite popular and it's time to really clean up my c++ while we're getting tooling / production sorted. Sure, I've written a fair bit all the way back in college but most of my day-to-day is in JS and Elixir.

I've had a great time reading through the Flipper Zero repo, but I'd love to see other fantastic (some might say Redis tier) open source C++ projects / production code deployed on ESP32 that could help me jog my skills.

Curious of what you all might suggest?

Thanks!