We're working towards accepting cash by mail in a month or two, and regarding cryptocurrencies, we've been trying to reach out to proxysto.re unsuccessfully for that. If you know of a similar option, we'd love to hear about it!

If the goal truly is privacy, and that's why you're adding cryptocurrency options, then adding a middleman like "proxysto.re" or any other, then you're not giving users the privacy you say you want to give. You really need to handle that on your end, if that's something you want to offer for the purpose of privacy.

Take a look at how Mullvad implemented it, which I guess is where you got the "cash in a letter" method from, they also handle cryptocurrencies by themselves for exactly this reason, there is no way for you to actually be able to fulfill the privacy promise otherwise.

Privacy Pass would also be a good option. You can use it with Kagi, where you’ll have cryptographic tokens that you can use for searches without them being linked to your account. Even if you use a non-anonymous payment method, you could still use the service without leaving a trace.

I have to agree with embedding-shape, don't use a middleman please. Just accept monero payments yourself <3

Once you accept Monero I'll give it a try :)