Ok, this might be a dumb question, but is it really technically possible in any way - even a convoluted one, like manually downloading HTML pages from Facebook? - to mass import posts from one’s Facebook into Mastodon or Friendica instead of painstakingly copying them one by one? I’ve got a 10+ year archive to port and it’s a daunting task to go through them…
That sounds like a good approach. If you can get the posts into WordPress, there’s so many scripts out there that will export the WordPress database into other formats.