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