The relevant one is -
No cross-posting adverts you've put on other sites. If you have an item for sale anywhere other than here, like ebay, bikeradar, ctc, retrobike, etc. then you cannot post it here. However, if you have posted it on one of those other sites, other people who have discovered it are allowed to post it in the eBay/Craigslist finds thread. You must not do this yourself.
The rules from 9 years ago as I know them are -
https://www.lfgss.com/conversations/143848/#6571218
The relevant one is -
No cross-posting adverts you've put on other sites. If you have an item for sale anywhere other than here, like ebay, bikeradar, ctc, retrobike, etc. then you cannot post it here. However, if you have posted it on one of those other sites, other people who have discovered it are allowed to post it in the eBay/Craigslist finds thread. You must not do this yourself.