Earning interest on BTC is against the very principle of Bitcoin.
You get interests on fiat deposits, as they are not protected against inflation. The interest payment is made, in order to compensate you for the decline in the purchasing power of the fiat currency. However, the purchasing power of Bitcoin will not decline with time (due to controlled supply), and therefore interest payments don't need to be made for deposits in BTC.
This. The mathematics of Fiat currencies work to primarily support the subject of interest. Since there is nothing to back Fiat currency against i.e a limited supply of Gold or something like that, there exists a potential for Fiat currencies to expand indefinitely. Banks and credit cards are two channels that create "credit" in our financial system and the idea of "interest" is an invention from that.
Unless you found a provider who privately took on Bitcoin loans from other people and reinvested their money into ROI profitable businesses so that everyone benefitted, it would be difficult to find a place to obtain true "interest" on your BTC.
IMHO the best way earn interest from your Bitcoin is to set up a Bitcoin mining rig
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