Google just announced that they are going to start turning off v2 Chrome extensions in June 2023.
The problem is a ton of the examples and code out there uses a v2 manifest.
I personally have had a hard time with the new change where you can't load external javascript via tags. That made me learn npm and webpack and serverless functions etc.
Here is their article on how to migrate - https://developer.chrome.com/docs/extensions/mv3/intro/mv3-migration/
And here is their proposed timeline for moving to v3. - https://developer.chrome.com/blog/more-mv2-transition/