bash 5.2.x + ternary operator: How can I use this combo when checking if my string variable is empty or not?

I have tried

myvar1=[[ -n "$distro" ]] && echo $distro || echo "debian"

myvar2=$((- $distro ? $distrp : "debian"

the first one generates this error: -n: command not found

2nd one generates this error: expression expected (error token is “: debian”)