I've spent time with a few gentlemen who have had similar life changes and they generally let me know in the first few messages.
1 particular gentlemen sent along this article when he told me, second message. I"https://www.vice.com/en/article/y3m39k/sex-with-an-ostomy-bag-tips-and-interview-with-a-couple
t's about committed partners so of course the stuff about love and long term relationship isn't applicable but it helped me understand the realities of being intimate with s stoma and some of what he is dealing with.
It's up to you how much info you want to share and how early. But I think it would be good to know as early as possible if a potential SP is someone who will make you feel relaxed and comfortable, or if she's someone who won't. This line sums it up, "When one partner is not secure or comfortable with having the appliance in their lives, it reflects onto the other partner."
Finding someone who won't make you feel bad is, from my POV, an important part of choosing an SP so discussing it early enough to figure that out seems like a good idea.
The article also has some tips for resources and items that might make you, and her, feel more comfortable if you haven't yet started to look into that.
I think bottomline, you should feel good in every possible way and how that happens is entirely up to you.
Cheers