Well craigslist in my area is kinda dead so Facebook market place is the only place to do local buying and selling. It also acts as a lowest common denominator, I find someone on facebook send a few messages until we agree on some other social media to continue communicating on. Then My family uses What's app and has done since before they were acquired by meta. Getting them to switch is something I push for, but I'm not holding my breath.
There’s also Nextdoor, but fuck that noise with all the nimby and boomers on that platform “omg I saw a weird guy that was…. walking! Should I call the police?”
Edit: I typed “doomers” and it autocorrected to “boomers”, I’m leaving it