Have you tried to use "document.addEventListener('turbo:load')" instead?

[qwadrox]

https://github.com/softvar/enhanced-github/blob/e245d813d95faeebc06e07b6eb6fdd72eef60d19/src/background.js#L9C1-L26C1

turbo:load is an event that's part of Hotwire's Turbo which GitHub uses for its client-side navigation.
It's similar to the traditional DOMContentLoaded event, but specifically for Turbo-driven navigation as I understood.
https://turbo.hotwired.dev/reference/events#turbo%3Aload

document.addEventListener('turbo:load', () =>
{
  console.log('turbo:load')
   const titleSpan = document.querySelector('.gh-header-title .f1-light')
})

you wouldn't need any extension permission. it works just like dom content loaded.