I've been looking to pickup 25+ acres, preferably with some pasture on a large creek or small-medium river in Central/SC KY, something I can put a canoe in. I've been looking for a couple of months now but it seems like the only listings I can find are either Subdivision plots or massive tracts of land way out of my price range. I can't find anything in this area online (although there's plenty if I want to leave the area) and real-estate agents don't seem interested if they can't look it up on Zillow. The best suggestion I've heard is to start driving the backroads looking for "land for sale" signs. How do you guys find remote riverfront acreage? I'm looking for land to start my "retirement farm", not pay 10x actual value and deal with HOA BS. Any suggestions?

Property with good river frontage doesn't come up often.

I'd watch Whitetail Properties and Mossy Oak Properties.  If you're a serious buyer, contact either of them and tell them what you're looking for.  I expect a lot of prime properties never make it to listing due to a buyer ready to go.

Green River and it's big tributaries between Campbellsville and Munfordsville is holy grail of KY river frontage.

Take this with a grain of salt, but my mom and stepdad had a cabin near the red river that flooded twice in 16 years.  Most of the time, the Red was pretty tame, until it wasn't.

A lot of the real estate I've been searching for on realtor.com will tell me what the flood potential is especially if it is near the Licking River, the Kentucky, etc.

I've been looking in Lawrenceburg, Willisburg, Lancaster, Danville, Junction City, Liberty, Stanton, Stanford, Winchester, Carlisle, Irvine, Mount Olivet, Cynthiana, and Berry.

There isn't a lot out there right now and 25 acres will probably run somewhere in the $200-300k range.

Check this place out. Not sure if they have lots as big as you want though.
https://fivestaracres.com/