That's a valid concern. This extension is open source [1], if you were to want to see what's happening under the hood.

[1] https://github.com/cavi-au/Consent-O-Matic

Thanks for the recommendation! I am indeed sketched out by most extensions that require the all-hosts permission but this one does seem pretty legit so I'll give it a shot.

This is a fair concern. The particular extension is developed by Aarhus University, which is a major university in Denmark. Not a guarantee it won't do anything bad, but it should give you more comfort than any random extension developer.

I’m sure anyone installing an extension to make it easier to be tracked doesn’t care what the browser extension is doing either.

There's a sense in which cookies can't do any harms besides tracking, while a browser extension can do much worse.