Is there anything that GCC is missing? Looks complete to me [0]. Everything besides modules is also there for C++20 [1]. I'm at an automotive startup and we've been using a few C++26 features since summer already.
Are you ISO26262-compliant and your software is ASIL-A or higher? If no, why would you care about MISRA? If yes, how did you qualify a recent GCC?
Safety-critical automotive software development depends on tool qualification, which is often a lot of tedious work. There must be a spec, there must be tests, there must be proof that the tests cover the full spec, you must have a process to inform users about bugs. There is no free compiler which provides this.
Not yet compliant, but working on it. There's quite a few ASIL-D components too. We don't use GCC but rather tip-of-the-tree LLVM. Embedded is a completely separate and different mess using whatever the vendor ships for a particular microcontroller.
So far our safety guys haven't seen any issues with tool qualification besides requiring everything to be documented and the whole system to be re-tested in case of any tool changes.
[0] https://en.cppreference.com/w/cpp/compiler_support/17 [0] https://en.cppreference.com/w/cpp/compiler_support/20