It's not a question of support, it's a question of defaults. Rust code exercises a single-ownership discipline by default, and you must opt-in to dynamic multi-ownership (via refcounting or otherwise). In languages that have pervasive dynamic multi-ownership by default (via GC, etc.), enforced single-ownership is instead opt-in, which means that you cannot expect code in the wild to use it. In Rust, you can expect code in the wild to exhibit a single-ownership discipline; that's just the prevailing style for Rust code, as encouraged by the design of the language itself.

In fact, we can see this "defaults matter" problem in Rust as well. Note that Rust by-default assumes that code is running in a context where a dynamic allocator is available, but allows one to opt-out of this ("no_std" mode). Code written for embedded devices or baremetal contexts uniformly opt into this mode, but because it's not the default, you can't just pull any old library off the shelf and expect it to work for you, so the ecosystem is much smaller and less mature. Defaults matter.