The command line interface for Sapling called `sl`, which is Git compatible, is fully supported by the team at Meta. You can file bugs and feature requests, etc, though the repository is a bit intimidating. It is only the non-Git server components (Mononoke, EdenFS) that are not yet really supported [1] but I think most people aren't really concerned with that, when writing a post like this.

For all intents and purposes, Sapling works very well, I think, and in some places it has a lot more polish, like the "isl" graphical interface, which makes things like rebasing and restacking incredibly intuitive even for new users. (I consider isl to be a significant advantage over Jujutsu, and I say that as a Jujutsu developer!)

[1] Though, Mononoke does support features like exporting Git repositories to remote hosts from the internal model; that's not really what people are looking for in a lot of cases though.