This is possible in Nim using the "soft real-time" GC with "GC_step Mode" see https://nim-lang.org/docs/gc.html. You can even tell the GC how much time it can pause.
> In fact, I see many similarities between Nelua and Nim.
I am the Nelua author, and I've used Nim for a reasonable amount of time before creating Nelua, thus Nim served as one of the inspirations for the project and they share similarities. But while Nim resembles Python, Nelua resembles Lua. Also when comparing both, Nelua tries to be more minimal and generate more readable and compact C code.
But Nim also has a new deterministic GC, that has been available since 2020 and will be the default in a future version, see: https://nim-lang.org/blog/2020/10/15/introduction-to-arc-orc...
In fact, I see many similarities between Nelua and Nim.