Unsubscribe link from their emails takes you to this. You then to need to sign in with email and password (I don't know my password) to manage preference. I just want all out!
What I do with these sometimes is replying to the e-mail itself with a message that has only the text unsubscribe in all caps. Might add that to the subject as well.
I used to manage an email queue that collected both GDPR requests and responses to marketing emails and saw a fair number of those. Many companies have it setup to forward responses to marketing emails to a support queue somewhere, but some don't