There is a classified section here on the Eagles Den where you could list it. I don't know that it sees a lot of traffic, but it's a place to start. Include lots of pictures and information about the car, including miles on it and where it is located.
There are several online options, including Craigslist, Facebook Marketplace, eBay, Bring a Trailer, etc. Craigslist and Facebook are the least complicated, but the others MAY bring you more money.
Do some research on what your car might be worth. You can look on eBay and Bring a Trailer to see what is listed now and what has sold and at what price. Do your homework so you don't sell it too cheap, and also to not overestimate what your Eagle might be worth. Some people are really into Eagles, others not so much. So there may be somebody out there that is really interested in buying your Eagle for a good price, but there probably won't be 20. I'm not saying this to discourage you, just trying to be realistic. And this is just my opinion, others may feel differently.
Good luck with the sale!