If you can get an Aussie, golden retriever, or a mix of those two I highly recommend them as decent farm dogs.
Golden’s have their spastic years 1 - 3 but if you have the patience to get past that you’ll have an excellent mom/dad dog of your flock, my old golden Bear treated the geese like they were his kids and protected the yard.
I’ve had good luck training my Aussie, and Aussie Golden mix to break up gander fights, if you teach them young not to be predatory towards birds they never develop that trait and only make sure everyone behaves. The other plus is that they’re the best ratters I’ve ever seen.
My other current farm dog is a Boerboel, I would recommend them as a farm dog because #1 highly intelligent, I haven’t had to teach him not to be predatory towards the birds, he just gets they’re his family because Boerboels are specifically bred to be farm dogs. #2 Boerboels are so massive and deep voiced hardly anything predatory wants to come in the yard anymore. #3 He’s very well behaved.
Reasons I would NOT recommend a Boerboel is #1 the price. #2 they’re starting to get popular and because of their looks “large mastiff type” they’re starting to be bred by scums as “attack dogs” and not every Boerboel is a real Boerboel now. If you see a breeder showing off how “aggressive” their dogs are, avoid.
Note that not every individual in a breed has the same attributes, some swear by German shepherds as flock guardians, the three I knew were bird killers. People consider Labs as the typical family dog, my parent’s lab tried to kill me. People are terrified of Ovcharkas, I grew up with one, no issues. It all comes down to personality which is hard to gage, but if you find one with a family history of being around livestock you’ve got a good chance of having an excellent dog.
Also it may be an unpopular opinion but if you know what you’re doing you don’t have to fix your dog. My two females 9 & 8 years old aren’t fixed. My Boerboel isn’t fixed. My Golden who passed away wasn’t fixed. The only dog I had that was fixed passed away due to complications of being fixed. If your female is going into heat just keep them inside, supervise them when out, it can be annoying for some but it isn’t that hard to keep them from breeding. Not fixing a female can lead to hormone issues that can cause cancer, but fixing them can do the same, so it’s up to you to judge wether it’s worth it based on that.