Squarize everythings.

SQ.user.js

// ==UserScript==
// @name SQ
// @namespace Violentmonkey Scripts
// @match *://*/*
// @grant none
// @version 1.0
// @author koumaza
// ==/UserScript==
const sqz=(e)=>{
  e.style.setProperty('border-radius','0','important')
}
const replaceElemTag = (sourceElemParent, targetTag, beforeTag) => {
  return sourceElemParent.innerHTML
    .replace(`<${beforeTag}`,`<${targetTag}`)
    .replace(`</${beforeTag}>`,`</${targetTag}>`)
}
const replaceElemTagByOuter = (sourceElem, targetTag, beforeTag) => {
  return sourceElem.outerHTML
    .replace(`<${beforeTag}`,`<${targetTag}`)
    .replace(`</${beforeTag}>`,`</${targetTag}>`)
}
const replaceElemTagAll = (targetTag, beforeTag) => {
  let elems = Array.apply([],document.getElementsByTagName(beforeTag)).map(b=>{return b.parentNode})
  elems.map(p=>{
    p.innerHTML = replaceElemTag(p,targetTag,beforeTag)
  })
}
const applyAllAttrs = (attrs, elem) => {
  let e = elem
  attrs.map(a=>e.setAttribute(a[0],a[1]))
  return e
}
const sqzRect = (e) => {
  e.removeAttribute('rx')
  e.removeAttribute('ry')
  e.style.setProperty('shape-rendering','crispEdges','important')
}
const chkNaN = n => {return !isNaN(Number(n)) ? Number(n) : ''}
const sqzCircle = (e) => {
  let attrs = [...e.attributes].map(a=>[a.name,a.value])
  let a = applyAllAttrs(attrs,document.createElementNS('http://www.w3.org/2000/svg', 'rect'))
  let r = chkNaN(e.getAttribute('r'))
  let l = chkNaN(e.getAttribute('r')*2)
  a.setAttribute('width',l)
  a.setAttribute('height',l)
  // a.setAttribute('rx','')
  // a.setAttribute('ry','')
  a.setAttribute('x',chkNaN(e.getAttribute('cx')-r))
  a.setAttribute('y',chkNaN(e.getAttribute('cy')-r))
  a.removeAttribute('cx')
  a.removeAttribute('cy')
  a.removeAttribute('r')
  a.style.setProperty('shape-rendering','crispEdges','important')
  a.constructor = SVGRectElement
  e.parentNode.replaceChild(a, e)
  
}
const sqzEllipse = (e) => {
  let attrs = [...e.attributes].map(a=>[a.name,a.value])
  let a = applyAllAttrs(attrs,document.createElementNS('http://www.w3.org/2000/svg', 'rect'))
  a.setAttribute('width',chkNaN(e.getAttribute('rx')*2))
  a.setAttribute('height',chkNaN(e.getAttribute('ry')*2))
  // a.setAttribute('rx','')
  // a.setAttribute('ry','')
  a.setAttribute('x',chkNaN(e.getAttribute('cx')-e.getAttribute('rx')))
  a.setAttribute('y',chkNaN(e.getAttribute('cy')-e.getAttribute('ry')))
  a.removeAttribute('cx')
  a.removeAttribute('cy')
  a.removeAttribute('rx')
  a.removeAttribute('ry')
  a.style.setProperty('shape-rendering','crispEdges','important')
  a.constructor = SVGRectElement
  e.parentNode.replaceChild(a, e)
}  

const doSqz = () => {
  Array.apply([],document.getElementsByTagName('*')).map(e => {
    sqz(e)
    switch (e.tagName) {
      case 'rect': sqzRect(e);break
      case 'circle': sqzCircle(e);break
      case 'ellipse': sqzEllipse(e);break
      default: break
    }
  })
  // Array.apply([],document.getElementsByTagName('iframe')).map(i=>{
  //   Array.apply([],i.contentWindow.document.getElementsByTagName('*')).map(e=>sqz(e))
  // })
}

window.addEventListener('load', () => {
  doSqz()
  setInterval(() => {
    doSqz()
  }, 500)
})

const s=document.createElement('style')
s.innerHTML=`*,:before,:after{border-radius:0!important;}`
document.head.appendChild(s)