Doing a quick google search, there's a few (granted, I haven't tested out, and i have never used these services):
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https://lordmancer2.io/-
https://thecryptocollectors.com/There's also many Minecraft servers which attempt to leverage cryptocurrencies as in-game currency. Some have actually been quite successful in doing so.
You obviously only read the Title and not the content of the OP's thread, right?
OP is looking for developers of RPG games, linked to Crypto currencies. OP is not looking for RPG games that supports Crypto currencies.
There are currently a massive shortage of game developers that knows something about Crypto currencies and the developers that do know about this, is busy with their own projects. <I know, because I asked around a few weeks ago for a friend who had a good idea for a game.>