On Bluefin, fish gets Homebrew via /usr/share/fish/vendor_conf.d/ublue-brew.fish which runs brew shellenv. Nushell has no equivalent.

Add to ~/.config/nushell/env.nu:

$env.HOMEBREW_PREFIX = "/home/linuxbrew/.linuxbrew"
$env.PATH = ($env.PATH | split row (char esep) 
    | prepend "/home/linuxbrew/.linuxbrew/bin"
    | prepend "/home/linuxbrew/.linuxbrew/sbin")

Then regenerate tool configs:

zoxide init nushell > ~/.zoxide.nu
atuin init nu > ~/.cache/nushell/atuin.nu
starship init nu > $(nu -c '$nu.data-dir')/vendor/autoload/starship.nu