Is there a way/product to trade BTC leverage on exchanges without paying funding every 8h?
I believe you are basically talking about the transaction fees with the futures trading, well, I've ever thought of this before, It's a negligible amount you shouldn't worry about as well. But if you are so desired for a reduced transaction fee, you might want to consider changing an exchange. I do hear good news about MEXC in terms of the transaction fees, you might want to try your luck with them also.
However, the two most important things I consider more than anything else in my crypto trading are the trust of the exchange/broker and the number of years I've used them without them failing me. I base these factors more importantly than the amount they charge me and I urge you to consider this.
After all, the average charges I know are not much, not for someone like me who has been well exploited by traditional brokers in the past.