I think this is the right answer. Having an instrument that you love to play will inspire you to practice and learn.IMO, it’s whatever uke gives you confidence and inspiration to keep playing. A uke with horrible action, not enough frets, or even high G vs low G can greatly impact how far takes themselves in learning the uke.
I think it is more a matter of having an adequately nice instrument than having the one you "just have to have." But perhaps having an adequate instrument can be taken to mean that you already have a "gotta have" instrument and therefore don't need another.Even if you buy a “beginner” uke, if you quickly find another online that you JUST HAVE TO HAVE, it could impair your willingness to keep going until you have THAT uke.
In any case, I find I most play the instruments that I enjoy playing and therefore those are the ones I make progress on.