"i.e." doing a lot of work there.
GDPR doesn't require pop-ups or banners for providing consent. It mentions "ticking a box when visiting an internet website" as an example implementation. But it's just there as an example.
https://gdpr.eu/Recital-32-Conditions-for-consent/
the mechanism for gathering consent is an implementation detail left to the site to handle because GDPR applies to far more than websites. i've had to provide consent for things completely unrelated to websites.
you could add a line of text saying "please write us a letter with the following information (user account, blah, blah) if you are willing to provide consent for optional tracking like blah blah" and this is perfectly in line with GDPR.
sure, it's more expensive and you'll get fewer people who you can track. but make no mistake, sites make a decision and choose pop-ups/banners as their implementation for gathering consent because they don't want to lose out. they're happy inflicting pop-ups/banners on their users instead so they can keep their precious tracking cookies going.
i.e. GDPR doesn't require pop-ups/banners, sites choose pop-ups/banners.