Can we collect consent for a group of websites or is consent always limited to a website?

If you'd like to share consents across multiple domains, you would first need to inform correctly the user on the notice (we can help there by checking your wording) and then we'll help you config the banners accordingly so that consents are stored on a 3rd party domain (like mycompagny.privacy-center.org).

Then if a user consents on a first website, he/she will not have to see the consent message again.