Another option instead of using Rc/Arc is to use integer indices/handles into (e.g.) a vector holding your objects. Then you can have safety (in the sense of there being no language-level UB) by bounds checking your indices (you can do even better if you use a generational arena and attach a generation counter to your indices), and you can still have arbitrary object graphs that way.

I think that this pattern is common in C++ game programming as well (e.g. when using entity component systems), because using pointers or references everywhere and building complicated object graphs is a recipe for object lifetime issues.

I would be surprised if anyone could handle the mental complexity of managing ownership in arbitrary object graphs without there being some simplifying idea (like that of an ownership tree) involved, even if it's not enforced at the compiler level (as it is in Rust, but it isn't in C++).