We pre-allocate a bunch of static buffers and re-use them. But that leads to a ton of ownership issues, like the append footgun mentioned in the article. We've even had to re-implement portions of the standard library because they allocate. And I get that we have a non-standard use case, and most programmers don't need to be this anal about memory usage. But we do, and it would be really nice to not feel like we're fighting the language.
I've heard the term "beaten path" used for these languages, or languages that an organization chooses to use and forbids the use of others.
If you use vanilla rust with global alloc everywhere then you will get fragmentation
You have to use nightly for custom allocators and implementing allocators and using them is super annoying still.