If you use Facebook, there is a Feedback and Inquiry group for reptiles there that you can search. https://www.facebook.com/groups/Rept...kandInquiries/
If you see a breeder with animals you like (on morphmarket or anywhere else), search the name and see if they have reviews. If there are bad reviews, you can avoid them, or mixed and you can evaluate yourself based on the contents of the reviews. If they're absent in the group it isn't necessarily a bad thing, and you can post asking for opinions and people usually can chime in good vs bad then.
Alternatively, you can search by species in the search bar also and look at "good guy" reviews for breeders of the species if you need help finding names to look into.
I believe there is still a similar board on the FaunaClassifieds forum (it went paywall at one point, but I think it is free again right now?).
I got one of my corns from Snakess n Lizzards and had a good experience with them, but I almost always purchase in person at local expos, so I have not ordered online for snakes before. https://www.facebook.com/SnakessNLizzards/
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