telemetr.io is basically a website that serves as a catalog for Telegram Channels. This website has at least 8.9 million channels and chats, which include adult contents.

Link: https://telemetr.io/en/channels

Telemetr.io comes with a helpful filter tool that allows you to search for the kind of content you want.
NOTE: You need to create a free account to use the filter function 

Select "Erotic" from the categories

It is optional to choose the country. But it is useful if you want something specific.

Not a must to choose USA, you can choose any country you want.

You can close the filter once you are done and the search results will be updated.

Enjoy beating your meat!

There's also a search feature that allows you to key in keywords.