Not subreddit but this one does the trick: https://startupgraveyard.io/. Source: almost 3 years ago

We went through gooddog.com to find our pup (cavapoochon) which we will be bringing home May 23rd! We had a really good experience with the website, they screen the breeders and follow up on your experience etc. The breeder we are going with found on the site is awesome. She constantly gives us updates via pictures and is even willing to meet us halfway to pick our pup up. Source: about 1 year ago

I bought my puppy from a breeder I didn't realize was kind of sketchy. She promised me papers and parents DNA info on pickup but "suddenly realized the sire didn't have the DNA registered with AKC". It's been 6mo since we got her and shes now ignoring me on gooddog.com. She says she chipped all the puppies with her own information but still hasn't provided a transfer of ownership. Source: over 1 year ago

Are the online puppy markets legit such as the puppies.com, gooddog.com or puppyfinder.com? I'd prefer to go through a breeder with a good reputation and hesitant to use one of the sites where it might be a puppymill or not the best of lines. Source: over 1 year ago

SOMETIMES I found good breeders through gooddog.com though, you have to be careful and make sure they're doing at least "Great Level" health testing. Source: over 1 year ago

I found a web site called https://gooddog.com that had a search for mixed breeds and came up with a list of contacts based on your zip code. Source: about 2 years ago