Their choice is actually Swift and by the time there's a stable release all the C++ code is intended to have been replaced.
Time will tell if that will be a big problem or if more mainstream ways of doing things are better for a project intended to run everywhere!
I remember they mentioning Swift a few months ago, but currently I don’t see any swift in their github repo, didn’t checked other branches besides main.
> all the C++ code is intended to have been replaced.
That is not their goal at all, I don't where you heard that. Swift is currently stalled due to some blockers listed on their issue tracker, but any usage of it will be in safety-critical areas first and not a complete rewrite of existing code.