I took a brief skim through so apologies if I missed that it was mentioned, but wanted to bring up the Embedded Template Library[0]. The (over)simplified concept is: it provides a statically-allocated subset (but large subset) of the C++ standard library for use in embedded systems. I used it recently in a C++ embedded project for statically-allocated container/list types, and for parsing strings, and the experience was nice.

[0]: https://www.etlcpp.com/