You will not be that lucky to get rid of idiotic signature campaign posters like that.
I found some information for you, according to
https://whitepaper.localethereum.comRATCHETING ADDRESSES
Each address in a LocalEthereum wallet contains an assigned index number beginning from zero. This index number is known colloquially as n. There can’t be any skipped indices.
Each LocalEthereum wallet begins with a random 32‐byte seed known as the zero‐index chain key (chainKey0). The seed can be used to determine the private key for the wallet’s first address (address0) and any subsequent addresses, making the system a deterministic wallet.
The private key for addressn can be determined from chainKeyn, and chainKeyn can be determined from chainKeyn‐1. Hence, if you know chainKeyn then you can determine addressm, where m is any number between n and infinity.
For this simple ratcheting algorithm, we use a common one‐way hashing function called HMAC‐SHA256. The calculations are as follows for every n-index chain key:
The n-index address private key (addressn) is HMAC‐SHA256(chainKeyn, 0x0001).
The next chain key (chainKeyn+1) is HMAC‐SHA256(chainKeyn, 0x02).
The page goes on to explain how the lowest chain key is backed up and not your older addresses, but I don't think there is any information on how to import this chain key or where to import it. I will search more and let you know here if I find anything.