Friendly heads-up: it's considered unwise to use a non-unix compliant shell as your login shell. Rather configure your terminal emulator to use nu as its shell - or go through the effort of invoking it each time if you're not in a GUI.
It's simple: there's too much code out there that assumes the login shell is Unix compliant. Remember that shells have been going out of their way to be Unix compliant for a very long time, rethinking the shell is a relatively new concept.
Quick question: what does “Unix compliant” mean in this context?
There are shells that are bash compatible, and shells that are sh compatible, and shells that work on posix systems, but I’m not sure what “Unix compliant” means.
I think you mean bash/sh compatible, as pretty much all code on the internet assumes that (a big reason why fish never really took off), and if you are putting things in .profile that expect bash (or sh) compatibility, and your shell doesn’t support that, it could do weird stuff.
