Accod. to the guide, I have to deposit the ERC20 to one of the exchanges, and the exchange will do the swap, but those mentioned exchanges have stopped support this swap.
I wonder why isn't there a non-exchange swap...
Have you tried all of them? If not, check it one by one. For example gate.io, you must have an account to see BTM_ETH in your wallet and be able to send the erc20 BTM.
Aside from the exchanges they've given in that tutorial, I don't think there's another way to swap.