If one's motivation for using green energy is to make the environment not go to crap as fast, then using green energy to mine crypto doesn't help anything and the use of green energy is nothing but a fig leaf.
If one wants to mine crypto, then do it as cheaply as possible instead. It really doesn't matter what the source of energy is. The entire system of crypto mining is inherently about who can use the energy the cheapest. Whats more, if someone gets energy cheaper it forces others to consume more power too.
If crypto is mined, it really doesn't matter what it uses power it - mining crypto is still increased consumption of power. Someone else is going to have to use non-green energy to do whatever they're going to do.
Energy production is not zero-sum with some fixed amount of non-renewables.
If I install solar on my house, I'm not forcing anyone else to use non-renewables. If I then use that solar to mine crypto, I'm... still not forcing anyone to use more non-renewables.
The person I was replying to said that mining was destroying the planet. This doesn't seem particularly true to me if you're mining on renewables.