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Well, try searching https://duckduckgo.com/?q=unity+portmone&ia=web and be surprised ;-)  *

Anyway, portmone means wallet and if you search unity and wallet, a lot of crypto things come up. And not https://www.portmone.com.ua/

You can post your support channels on your profile and your game page. There is no reason not to link to them in your games too.

If you do however make playing the game dependent on paying you, you should be clear about that in the game description. "Integrating" payment into a game usually means in-app purchases, drm and a lot of other things. Simply showing links to send money your way is not integrating.

And I am not quite sure if you can host a version that can only be played with external payments. If you have that, you should include a demo version that does not need the external payment system.

Most things should be explained in the faq.

https://itch.io/docs/creators/quality-guidelines#avoid-obtrusive-advertisements-...

https://itch.io/docs/creators/quality-guidelines#avoid-only-uploading-keys-or-li...

* For future readers: this very thread comes up first.