this archive link is floating around on blind and reddit. I have no idea if it's authentic. I didn't find a link to his other social media but the part about back pain lines up with this bit I found in a nymag article [0]

> Something seems to have changed in recent months. Martin told a Hawaii publication that his friend had suffered chronic back pain and texted him images after getting surgery before going “radio silent” over the summer. Asked in court if he was in contact with family, Mangione said “until recently.”

[0] https://nymag.com/intelligencer/article/luigi-mangione-unite...