"All of these languages have different syntax and semantics from C, only interoperate indirectly with C, and are not systems languages because of restrictive memory management or garbage collection."

Sorry, but Rust, Ada, and D are definitely systems languages.

Low-level programming, operating systems, and embedded systems have been created in each to various degrees.

C for All looks interesting, but disregarding these languages as "not systems languages" because they are not C is disingenuous.

It sounds like they re-invented Cyclone.

https://cyclone.thelanguage.org