F#. I hate the syntax, but anyone who enjoys ML will like it. Curly braces are optional.
It also meets all of your other requirements, including the "isn't strictly functional" part (which is somewhat rare).
Scala has most of these qualities, but people say it's extremely complicated and supports too many different paradigms in a single language. I've never used it.
I'd second F# and also in the same vein recommend Ocaml, in particular, if fast-running native code is a requirement. I haven't benchmarked it enough but I suspect that in most cases Ocaml might be a good deal faster.
I'm also very sympathetic to the non-functional aspects. I think being able to write imperative code easily (and it's surprisingly pleasant in ocaml/f#) is a huge plus.
As always, take these numbers with a grain of salt, but benchmarks seem to suggest that F# on .NET Core is significantly faster than OCaml [1]. I wouldn't be surprised if that were the case myself given how much work Microsoft has put into optimizing .NET Core for performance.
Why do languages make anything optional? It just leads to confusion and unnecessary style friction. I'm not saying everything should be as strict as Go, but... well, nothing should be optional.
In this case, I have no idea why they did it. Maybe to ease the transition from C-like languages to an ML language. I personally have never seen anyone use braces in F#.
Optional syntax is not at all rare, though.
Examples from various popular languages: white spaces, braces around single statements, trailing commas in lists, inferred type declarations, and parentheses.
There are also multiple ways to write things, like if...else vs. ternary operator vs. pattern matching vs. switch, often in the same language (C# has all of those, with pattern matching only being added recently due to demand).
I agree that I'd prefer that there only be one way to do things, but that's easier said than done. Sometimes users demand new syntax for different contexts or for the sake of terseness.
You can build arch-specific, single file binaries, but I believe the bulk of the executable is a zip file with the .net core runtime and all of your platform agnostic assemblies, so it's not exactly native like you're thinking of
It also meets all of your other requirements, including the "isn't strictly functional" part (which is somewhat rare).
Scala has most of these qualities, but people say it's extremely complicated and supports too many different paradigms in a single language. I've never used it.