There's also the Ravenscar profile[1] for Ada and the SPARK language[2]. How those compare in marketshare to MIRSA C, I'm not sure, I'm not in that field, though I've enjoyed reading about them at a conceptual level.
[1] https://en.wikipedia.org/wiki/Ravenscar_profile
[2] https://en.wikipedia.org/wiki/SPARK_(programming_language)
[&] https://docs.adacore.com/sparkdocs-docs/Examiner_Ravenscar.h...