There were some instructions in the first page of this thread
https://nxtforum.org/debune/erc20-debune-tokens-swap/NOTICE FOR THOSE THAT DON'T WANT TO USE ERC20 / ETHEREUM. Update:
A) Some of you have contacted me asking how to avoid the swap with the ERC20 tokens and swap directly with the DeBuNe blockchain tokens.
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Case A) I am open to this possibility, and I apologise for not thinking about it beforehand. In this case return the AE token from an Nxt account you will be able to use in the future to send me the DeBuNe blckchain account where I will send the matching DBN.
I can see there are some accounts which transfered back the DeBuNe assets to NXT-GQ27-DD53-YM6K-ER6HK without attaching any message with the ERC20 account in the attached message, so I believe all of them didn't want to go through the Ethereum step for the swap...