I'm an active website flipper and here are a few suggestions based on my experience:
Option 1: MotionInvest
They specifically deal with small to medium sites and have a nice pool of buyers. There are two options: first, they'll either buy your website directly or second, list it to the marketplace (20% commission)
Option 2: Facebook Groups
If you want to handle it all yourself and not pay any commission, this is better.
https://www.facebook.com/groups/flippingwebsiteshttps://www.facebook.com/groups/2422978371257718
You'll get plenty of interest but 80% of those will be just asking for domain and then won't reply. So, that's the worst thing but it's free so worth a try.
Make sure to always use Escrow.
Option 3: Flippa
I know everyone here thinks that Flippa is a rat hole (which it is) but there are some good buyers too.
https://www.blackhatworld.com/seo/a-little-trick-to-find-out-what-people-are-buying.1266904/
You can see here that the websites do get sold for a nice multiple so it's worth a try..
Option 4: BlackHatWorld
Yes, you can sell your website right on this forum and there are high chances that it'll get sold at a nice multiple here.
The only thing is that you'll need to wait for around 30 days (or more these days) to get the sales thread approved.
Good luck
