On the other hand, if you have any cryptocurrency (Steem, Bitcoin, Ether), the rising price inevitably means you will get an interest on your original investment whether you want it or not.

I think there's a difference between interest earned through a loan, where you loan somebody $100 and they have to pay back a certain amount in principal every month plus a percentage of what they haven't yet paid, which is clearly forbidden in Islam, and capital gains made from investment. The way I see it, a cryptocurrency is a commodity like any other, and it is absolutely fine to buy some because you believe the value will increase. If buying cryptocurrency was wrong for that reason, buying gold would be equally forbidden. Thanks for the help though!