I should mention, that demanding tracking may well be okay in GDPR, in necessary contexts: for instance a banking service may have to do some natures of fraud prevention using tracking, perhaps of recent internet facing IP addresses used and may have a regulatory need to do something like this.
Also bear in mind that GDPR isn't the only law here. If you want to access data stored on a user's terminal (mobile device, laptop, etc), then you likely need consent too under ePrivacy: for example "Article 5" https://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX...