If your domain is registered on Namecheap you can try their marketplace to place your domain for sale

Namecheap Marketplace Namecheap is accepting Cryptocurrency

You can try Domain forums like https://www.dnforum.com/ and https://www.webhostingtalk.com/ and arrange Bitcoin payment, Bitcointalk has a section for digital goods and it includes domain and so are other Cryptocurrency forums like altcoinstalk.