For those pesky websites that disable scrolling. Fiend mode button available in the popup if you dare. Install using the following link: https://gist.githubusercontent.com/Erquint/051e173afc07440050ac04c493d4c8d1/raw/scrollfiend.user.js

scrollfiend.user.js

// ==UserScript==
// @name Scrollfiend
// @description Enables scrolling on those pesky websites that disable it.
// @version 2.0.0
// @namespace [email protected]
// @author https://gist.github.com/Erquint
// @homepageURL https://gist.github.com/Erquint/051e173afc07440050ac04c493d4c8d1
// @updateURL https://gist.githubusercontent.com/Erquint/051e173afc07440050ac04c493d4c8d1/raw/scrollfiend.user.js
// @downloadURL https://gist.githubusercontent.com/Erquint/051e173afc07440050ac04c493d4c8d1/raw/scrollfiend.user.js
// @match *://*/*
// @grant GM_addStyle
// @grant GM_registerMenuCommand
// @run-at document-idle
// ==/UserScript==

// StyleSheetList[CSSStyleSheet] sheets = document.styleSheets
// CSSRuleList[CSSRule]          rules  = CSSStyleSheet.cssRules
// CSSRuleList[CSSRule]          rules  = CSSRule.cssRules
// CSSStyleDeclaration           style  = CSSRule.style
// 
// document.styleSheets[0].cssRules[0].style
// document.styleSheets[0].cssRules[0].cssRules[0].style

function get_all_rules(){
  buffer_1 = Array.from(document.styleSheets);
  
  while(true){
    let buffer_2 = new Array;
    let sheets_found = false;
    
    while(buffer_1.length){
      sheet_or_rule = buffer_1.pop();
      if(!!sheet_or_rule?.cssRules && !!sheet_or_rule?.cssRules.length){ // Sheet.
        sheets_found = true;
        buffer_2.push(...sheet_or_rule.cssRules);
      }else{ //                                                             Rule.
        buffer_2.push(sheet_or_rule);
      }
    }
    
    if(sheets_found){
      buffer_1 = buffer_2;
    }else{ //                                                               All page rules are in buffer_2.
      return buffer_2;
    }
  }
}

function rampage(){
  const selector_string = ':root, html, body, main, article, *';
  const rules_string = 'overflow: unset !important; overflow-x: unset !important; overflow-y: unset !important; position: unset !important;';
  rules = get_all_rules();
  rules.push(GM_addStyle(`${selector_string} {${rules_string}}`).sheet.cssRules[0]);
  
  for(rule of rules){
    if(!!rule?.style){
      rule.style.overflow = 'unset !important';
      rule.style.overflowX = 'unset !important';
      rule.style.overflowY = 'unset !important';
      rule.style.position = 'unset !important';
      rule.style.cssText += `${rules_string}`;
      
      for(element of document.querySelectorAll(rule.style.parentRule.selectorText)){
        element.style.cssText = `${rules_string}`;
      }
      
      for(eventTarget of [window, document]){
        for(eventType of ['wheel', 'keydown']){
          eventTarget.addEventListener(eventType, e => event.stopImmediatePropagation(), true);
        }
      }
    }
  }
}

let rules;
GM_registerMenuCommand('Reinforce!', rampage);
rampage();