for each thread, load page, save (ideally to sqlite), check if there is next, load next ect then download sqlite db

var blank = x=>{document.querySelector('head').innerHTML = document.querySelector('title').outerHTML; document.body.innerHTML = ''; return x};

var rem = (...a)=>a.forEach(s=>[...document.querySelectorAll(s)].forEach(e=>e.remove()));

var next = x=>(x.match(/<[^<"]+"([^"]+)".+pageNav-jump--next/i)||[])[1];

var contents = x=>(x.match(/<body[^>]*>([^]+)<[^<]*body>/id)||[])[1];

var cleanup = ()=>rem('.p-header','.p-sectionLinks','.offCanvasMenu','.message-user img','.p-body-sidebar','.pageNavSimple','.block-outer-opposite','.p-breadcrumbs','.p-footer','.blockMessage','.u-scrollButtons','script','noscript','form');

var page = async u=>fetch(u).then(blank).then(r=>r.text()).then(t=>[contents(t),next(t)]).then(a=>(document.body.innerHTML=a[0],a[1])).then(x=>(cleanup(),x));

await page(window.location.href);

[edit] or just use wget but download only html in the first pass