Ask HN: What to do with digital assets of shutdown organization?

I am working with a charitable organization that is unfortunately shutting down. They are wondering what to do with their digital assets (eg websites, social media accounts, images, donor and volunteer lists, etc). My instinct is to archive them but I am wondering where to keep the archives (thumbdrive?) and how to handle any PII (email addresses, etc) to ensure it is safe long term. I'm curious if anyone has had to deal with this issue and what steps they took to handle digital assets of dissolved organizations.