Let’s not derail this topic with questions about the Windows console (which is particularly bad for Unicode because it doesn’t support fallback fonts). The original poster is on FreeBSD, and so presumably just needs to install a font (e.g. JuliaMono?) that supports the ν̂ glyph.
Terminal emulators vary a lot in their capabilities, particularly when it comes to rendering text in your selected font. For example, some will let you display ligatures, others won’t. Some can handle diacritic/glyph composition, some can’t. Others are working on improving support for various features, but haven’t got there yet. Others aren’t supporting features for performance reasons. (For example, browse the issues on Alacritty’s GitHub…)
So it looks like the combination of terminal emulator and font you’re using is not performing ideally. Trying various different combinations of terminal emulator and font isn’t everyone’s idea of A Good Time, but it’s probably worth trying a few, if you spend all day looking at it…!