I think at the moment, Binance might be the only popular exchange offering multi-asset mode for even retail traders. Bybit had a similar product last year (Unified Margin Account) but they suspended it for unknown reasons. Maybe they will bring it back in the future. The minimum balance require was $5,000
Try checking out Kraken futures platform (
https://futures.kraken.com/). I have never used it, but I recently saw multi-collateral futures contracts. I don't know the required limits, though.
Apart from those I don't know any other derivatives exchange offering such products, not phemex, not mexc...